Yes, Spotify could do both. But that wouldn’t solve the issue at hand here. Let me explain:
Spotify streams to the speakers. iPhone controls the playback. The stream never enters the phone. The main benefit to this is that music doesn’t stop if you leave the house, plus that a stream can (depending on the speaker) be initiated without even using the app.
Here’s the issue: Even if Spotify chooses to support Airplay 2, it only benefits speakers with Airplay 2. It does not fix the issue for Spotify Connect or Airplay 1 speakers. Those customers used to be able to control volume using the side buttons. Now they cannot, due to a change imposed by Apple, and Spotify CANNOT fix this issue by “implementing Apple’s API”. Because each of the speaker manufacturers would also have to do it, and in many cases this is not possible because the hardware is not capable.
This doesn’t even take into account that Spotify Connect offers certain features that Airplay doesn’t, or that Airplay 2 sounds worse. It would be great for Airplay fans if Spotify would support Airplay - sure. But it DOES NOT fix the issue at hand, so it is irrelevant. And it is poor journalism by MacRumors to suggest as much.
To be clear, I am not an engineer so I don’t know all the low level programming details. I do know the implications on cost, time to market, and not least limits on choice of SOC that supporting Airplay puts on the speaker manufacturer. Your last comment is, sorry, pretty ignorant. Do you realize the costs involved with adding an extra SKU? This is not necessarily worth the investment. And in any case, this is a decision made by the hardware manufacturer, not by Spotify. Plus, it won’t help the existing products in the market that are hardware limited. (Our speakers do support both, I am just saying that I understand why some don’t).
Look, I loathe Spotify for all sorts of reasons, and I fully understand why the auto-reply is to hate on Spotify. I do pay them, and five(!) other premium streaming services, for business reasons and because I have a specific use case where only they offer a solution (play back a playlist without access to a control device). But objectively, Spotify has no less of a right to decide which protocol their customer should use, than Apple. You can’t objectively say that it is okay for Apple to use their muscles to enforce a specific API, but not okay for Spotify to use their muscles to enforce a specific API.
I love Apple, and I mostly hate Spotify, but in this specific case, Spotify is right. Apple is trying to bully streaming services into using their inferior API.