I read them as agreeing with you, but pointing out that fixing bugs, at the end of the day, is up to the client.

It's just a predictable dance. You say something will take this long, then you find a bug. You point it out to the client, and they get mad at you because your estimate was off. They try to pressure you into fixing the bug for free, whether you were even around when it was made.

Eventually you just make a judgement call about bugs every time you run into them.