Absolutely right.
I scrapped one last year that looked pretty good, and passed the usual MOT sill squeeze test on one side, but failed on the other. When I took the sill covers off both sides were toast. The side that would have passed the MOT was slightly better, but still had 5 or 6 inches of rust hole on the outer, and both sides were pretty bad once the outer was cut off.
To do it properly would have cost double the value of the car, and it still would have needed dampers all round and caliper rebuilds on the front.
Owner was shocked when shown the state of it, as no other rust visible on car. Sadly Paintwork was a bit rough, 120k miles and interior was "lived-in", so not financially viable.
I did get some more parts for my own 100hp spares pile out of it, so some of it will live on.