See previous discussion in #52285. At that time the decision was to use symlinks, but that's kind of a pain due to dart-lang/pub#3143, which means all files have to be symlinked, rather than the directories (which wasn't true when the decision was made initially). For non-trivial plugins that can be a lot of files (e.g., in_app_purchase).

I'd need to look at the logic again, but I think it would be plausible to have a pubspec.yaml entry in the platform section that would allow opting into a shared directory instead of the currently hard-code ios or macos. If it's not too much complexity, I think the maintenance benefits for plugins would be worth the effort.

See also #114179

(/cc @jmagman for thoughts)