It helps in extremely niche scenarios where Tier 0 (on CoreCLR) is too slow or allocates too much, and it can't be crossgen'd due to cross-assembly types - though we might eventually work around that on the runtime side. Otherwise, it's a pure regression: there is no dynamic PGO, and it's highly likely that all statics aren't initialized at JIT time, meaning they are emitted with lazy-init helper calls, etc. Obviously, it has no impact on NativeAOT at all. Sometimes it might be used as a "don't use Dynamic PGO for this" hint, but there shouldn't be a good reason for that either.

Basically, in the entire BCL there is just one usage (see #90965 and #90899)