UFO Export Kerning

This is more of a question than issue, how come Glyphs app adds kerning to the feature file when it exports a UFO as well as in the kerning.plist? Which does Robofont read in the end?

There are so many different requirements what people will do with the .ufos. So having full feature code is important when you just like to export with fontmake.
I don’t know what Robofont does or doesn’t.

Thanks for that, one thing I noticed is when I tick decompose smart stuff, kerning is written to the feature file? But not if I don’t, I don’t tick it because it changes the starting point and messes up compatibility…