From what I've seen if an online store provides a 16 bit classic without a reimplementation, it's bundled with dosbox.

Of course, I'm pretty much blanking on any classic Win16 titles of note. As far as I recall the significant games just kept being DOS games with at most launch from icon. I suppose original Myst because QuickTime, but they released a Win32 build. But this 16 bit stuff was a speculation, this is about the 32 bit stuff that isn't reasonably accommodated without a 32 bit runtime and certain bits being at odds with Flatpak isolation architecture.