That crowd has the disadvantage of not being primarily interested in the other platforms, so they won't be much invested in optimizing or better matching the target capabilities.
That's the same dynamic as web devs writing React Native apps: you won't expect them to contribute extensions that manipulate local apfs metadata for instance.
So while it's nice to have them use the tools, you still need people who primarily care for non Apple platform and embrance swift for their purpose to have it expand.
Hmm Snowflake and Apple are rewriting FoundationDB in Swift. Swift has pretty good dev. ergonomics and good interop with C/C++ so it might find it's niche outside of Apple.
That's the same dynamic as web devs writing React Native apps: you won't expect them to contribute extensions that manipulate local apfs metadata for instance.
So while it's nice to have them use the tools, you still need people who primarily care for non Apple platform and embrance swift for their purpose to have it expand.