No, it's still behind a flag (and so transitively, exceptions are too, because we built exception objects on top of GC).

Our docs (https://docs.wasmtime.dev/stability-tiers.html) put GC at tier 2 with reason "production quality" and I believe the remaining concerns there are that we want to do a semi-space copying implementation rather than current DRC eventually. Nick could say more. But we're spec-compliant as-is and the question was whether we've implemented these features -- which we have :-)