I read the text, but you're removing the context. Here's the full quote:
Whenever you receive an alert or notification, or perform a function like turning the Digital Crown or pressing down on the display, you feel a tactile sensation thats recognizably different for each kind of interaction.
This implies that receiving an alert or notification is a kind of interaction, and thus has a recognizably different tactile sensation from other kinds of interactions. Ok, that makes sense. However, that doesn't tell you anything about how you perceive tabs from other people.
Like I said before, I don't know if you first receive a notification from the watch, tell you someone has a tap-message for you, or that you directly receive that tap-message without any standard pre-announcement. The latter seems more logical to me and it's also implied in the keynote and on the site, so that's what I'm assuming.
But let's split it up for arguments sake, and think through both scenarios:
1. You receive a (customisable) notification from the watch, telling you someone has sent you a tap-message. You look at the watch, accept the tap-message, see the sender's name, see the color and feel the tap-message, and interpret its meaning.
2. You directly receive a tap-message from someone. You feel a certain tap-message, but it could be from anyone. So to find out you look at the watch
after receiving the tap-message, see the sender's name, see the color,
need to remember the tap-message, and interpret its meaning.
Both aren't ideal, and both bring up some problems I mentioned earlier. Taps aren't a very broad language. Unless you know morse code, it's very difficult to remember a wide range of different messages. Also, simpel tap-messages are pretty much all the same.
So regardless of how you receive the message (scenario 1 or 2), you still need to remember what "three taps" mean for person A, if you're also using it with person B. You simply
cannot use unique tap counts for each contact because a) you probably have more than a few and b) you don't control how many contacts
your contacts have. Maybe you want to use "three taps" with person A, but they might already use "three taps" with person C.
The more people you know with an Apple Watch, and the more people
they know, the harder it gets to find tap combinations that both contacts only use with each other.
As for my original question: who's tapping? This only applies to scenario 2: you receive the tap-message from your contact directly, not after a notification that there is a tap-message. That would create even more confusion, because you simply can't think "oh three taps, that means lunch with person A", because it might also mean "bring milk when you get home" sent by person B. Or it might be person C who's just tapping away and it didn't mean anything specific.
Bottom line: if you feel taps, you need to look at your watch to see the name, color and then figure out what the heck it meant for this particular person. So that pretty much means that it's great to use with 1 or 2 people, if those people also only use it with you and one other person, and it's great for demo/keynote purposes, but when you use it with larger groups of friends it can get very confusing to use any of these tap-messages.
Also, from their Features page:
Tap. Let friends or loved ones know youre thinking of them with a silent, gentle tap theyll feel on the wrist. You can even customize taps for different people.
This doesn't tell us much definitively, but it implies that this is scenario 2: you feel the tap-message directly on your wrist.
But I don't know what "You can even customize taps for different people" means. You assume it means that you can create custom tap-feelings, just like you can create custom vibration alerts for your contacts on the iPhone. But that seems like a very hard thing to accomplish. Vibrations are created by the device itself, and can thus be very specific. How different can "gentle taps" on your wrist be?
If someone sends me three taps, how many different ways are there to let me feel those three taps? They're just taps taps. It's not a combination of 500 rapid vibrations in a few seconds and in very specific bursts. That's a huge difference. I think you run out of ways to do different "gentle taps" very quickly (gentle, very gentle, not so gentle), and definitely can't do this for that many contacts.
I think that "You can even customize taps for different people" doesn't have anything to do with that you, the receiver, can customise some kind of tap-feeling, but that it's about you, the sender, who can choose different colors as depicted on the image above the text and demoed in the keynote. This also matches with the beginning of the text "Let friends or loved ones know". They're talking about
sending taps.
The only thing I can think of is that the sender can tap on certain area's on the screen, so that the receiver also feels the taps on those area's. They mentioned something about the walking direction having taps on different areas to indicate left and right, so that's plausible. But the taptic engine part is smaller than the screen and round, so there isn't a 1:1 correlation between where you tap on the screen and where you feel it on your wrist. And I imagine that it's even harder to differentiate and remember where those taps were exactly as it is to remember what those taps mean from this particular sender. And it would be hard for the sender to always tap exactly in the right spot so that the tap is translated correctly by the receiver, and doesn't suddenly mean something else. All this seems
way too complicated.
