I have not read the NIP in detail, but the receiving wallet does actually post a sort of “read receipt” event that it got zaps. These could be aggregated by a relay for sorting (right now it just displays on the post).

I haven’t read enough about the NIP to understand how the zap gets communicated to the wallet - if that somehow happens in the lightning transaction or if the sending nostr client is also publishing a send event that the receiving wallet has to look for.

So definitely more going on than a standard tip, but I can’t say I fully understand it yet