If he engine does have 30K miles on it, there is a bit of taper and out of round in the bore, this is normal. But if the rings are “stuck” with a combination of carbon and old
oil (this stuff is like concrete!) they will not adjust to that taper as the pistons travel up and down. The carbon/
oil mixture will solidify behind the rings and prevent flexing and sealing. Some will be stuck in the position that is the smaller part of the bore (the bottom) and will not seal at the top causing blow by. And some will be stuck at the larger part of the bore, the top and this will cause rapid wear on the cylinders and can escalate into broken rings/scored cylinders very quickly (in minutes!).
I have seen this and I would tear it down, 428’s only rebore so many times…