The one nice thing about web browsers is that they have a reasonably formalized specification set and a huge array of tests that can be used. So this makes them a fairly unique proposition ideally suited to AI construction.
>>qingch+(OP)
As far as I read on Ladybird's blog updates, the issue is less the formalised specs, and more that other browsers break the specs, so websites adjust, so you need to take the non-compliance to specs into account with your design