That's a very good question.
The fact that as of March 2016 there's been 171 manufactured for the US and only 31 air-force pilots are represented is a little funny as well. (I would expect that they got pilot opinions throughout development/testing.) — One of the interesting things in the assessment linked in the article is how the comparison of the A-10 is in jet maneuverability
, but that's not the issue that is at hand for the push to replace the A-10: the A-10 was designed to go low-and-slow and have a high loiter time, so that it could do CAS (including tank- and APC-busting).
I don’t even understand how the F35 and A10 are remotely comparable.