You must know that breaking down and verifying someone else's analysis is more time consuming than writing your own. Just like dealing with a bug in another person's code.
Given them the benefit of doubt that Go team is cautious about binary size. People have dug in to this. Sure, they could do a better job giving some breakdown, but claiming that they are careless deserves that kind of response.
Given a choice of their time, I would rather have them work on some other Go language problem. Most low hanging fruit has already been had. See [1] [2] [3]