@PaQ thank you, of course I use it, and lately folks at Autodesk put lots of efforts to improve the Retopo modifier. There're hints that they will push it even further.
https://www.youtube.com/watch?v=qtj3rvL2pUI&t=161s
But its still doesn't mean Moi's exporter can't be improved :)

>>Hi rom, maybe I can detect these kind of n-gons and do some additional refinement just on them.
Awesome Michael, thank you for attention