This is somewhat technical and might be tricky to wrap a noggin around.

to get metadata privacy with giftwraps you make a fairly large tradeoff: you have to give up filting at the protocol level. you have to accept unmarked envelopes from anywhere. this can easily be abused and spammed, you have to unwrap the note to see who its from which has computational costs. so you could in theory DoS someone with lots of giftwraps and theres no way around that.

I believe semisol is saying that he would rather not make this tradeoff and just focus on tech that gives forward secrecy if he had to make the choice (correct me if I'm wrong)

They aren't mutually exclusive though, there are things like semisol channels where you could have fairly good metadata hiding and forward secrecy, but its a 1-to-1 thing instead of from anyone.