Do the "linuxisms" inherent in a compatibility shim like linuxlator get exposed to users in day to day application use?

I figured it'd be more like how proton provides windows APIs on Linux and applications "just work" as per normal.

I admire your purist approach, but most folks don't have that luxury and just need to make do with what works today for their tooling of choice (or more common, what their employer thrusts upon them.)

Compatibility layers can also introduce security bugs. One of the reasons why it was removed from OpenBSD.

BSD is more for purists anyway. Virtualization seems to be a better option than compatibility layers for the odd program that doesn't work natively.

Maybe that it's different for Windows API's on Linux, because by virtualizing Windows, you're still dealing with an unfree OS.