No, it comes up because it is one of the questions on the TA6 form.
Indeed, and if the seller lies when filling out that form, then that can come back to bite them - in very expensive ways.
If they don't admit that the CU was changed, then that's falsifying the information on the form. For transactions typically involving hundreds of £k, you really don't want to be doing that.
If they do say it's been done, and there are no certificates, then the buyers solicitor will go into auto-stop mode and flag this up as needing rectifying before purchase. Even if the buyer is happy to accept the risk, it'll delay things while the solicitors "discuss" it.
OK, for a CU change, assuming it's been done right, then it's not likely to be a problem. But I recall reading about cases where it was more serious, and it's led to some eye watering costs for the seller - technically, the buyer could be entitled to demand their money back if there's been a serious problem and the sellers information was fraudulent. Or the buyer could demand the seller pay all the costs of rectification - again, could be expensive is there are serious structural issues.
Of course, I would be rather wary if a seller said there had been no electrical works since (IIRC) 2005. Over 2 decades, no electrical works, raises questions for me. "Nothing notifiable", OK; "none", raises questions.