#description_display is ignored for fields

I don't know what I was doing in 2015, but since then I learnt to report better than this even if in a rush.

I think the key was adding #description_display to fields in form_alter, and I guess I hoped that the widget element would inherit that. Probably we can close it, as that behavior is not a pattern somewhere else, and if I was referring to something else I forgot what it was.

Or maybe even was a duplicate from #2318757: Make position of #description configurable via the API for form field widgets → . Anyway this should be closed.

Thank you!