His personal history contextualises his point, which is distinct from criticising his personal history at broad.

For example, had I said "Barry designed the new start UI. He also has received several speeding tickets" you could make the claim that I am making an ad hominem attack on Barry, since the only reason I would bring up the speeding ticket is to make Barry seem less responsible. His speeding does not affect his ability to design a start menu nor does it influence his design decisions.

However, if I said "Harry has been seen criticising the new start UI for being inconsistent. Harry previously designed the new Settings menu in Windows, which was also inconsistent", there are some important differences to take account of. Specifically, the fact he was involved in the development of another feature in the Windows product, AND it can also be criticised for the same failing that Harry has now applied to the start menu gives us information ABOUT Harry's criticism.

Now we can say "Harry is going to come at this from the perspective of someone on the team" and "Harry has made the same mistake before". Depending on the details of Harry's comment, that could make his comment less trustworthy, but conversely it can also make it more valid.

Calling that an ad hominem is, in my opinion, excessively reductive, and in the case of contextual data being added that is contextually relevant, not appropriate.