You don't ever have to install Yelp to use it within Apple Maps. The app does not come on the iPhone by default. By default it opens the Yelp website (which of course nags you to get their app and/or login, but that's not unique to Yelp).
You sure about that? For me tapping on any business info takes me straight to the iOS app store.
This would be due to a "universal link"; that's something that Yelp set up on their domain. It's possible that it wasn't there in the past, so you may not be misremembering at all.
You sure about that? For me tapping on any business info takes me straight to the iOS app store.