Because zaps (when you zap from the little button on a post) pulls a bolt11 invoice so Muun never actually sees the LNURL that way
Discussion
To say this more clearly, it’s a different flow with zaps. With zaps the client uses the LNURL to request the bolt11 invoice and then passes that on to the paying wallet. With a non-zap payment, the wallet must be able to pull a bolt11 using LNURL, which Muun can’t do.
