It isn't anytime you pass "a" starbucks. It is anytime you pass the specific starbucks you added to the favorite...
EDIT: Yes full wallet/passbook access from the apple pay screen would be great. This is how the phone is now, so I imagine it will eventually come on the watch.
In my case, I pass many of my "favorite" starbucks all the time. Sometimes I grab a drink, sometimes I don't... Multiple notifications when not needed in my situation =