You should check that out carefully. Often, consumer law does not protect you as strongly when the repair is paid for by the manufacturer as a part of an "original" warranty. I'm not saying you're incorrect, but I have seen this treatment applied before.
As the repair is made as part of the originally contracted 4yr/50K warranty, there may not be any legal requirement for the warranty to be extended past that point regardless of the mileage of the repair. The original warranty document is very clear that coverage ends at a certain period.
This of course does not apply to any repairs that you pay for.
1998 C230 "Black Betty"