I have said many times for many years. The most dangerous thing I do is an oil change. Make $10 profit on the chance we don't damage a $20,000 engine.
Personally I wouldn't mind if everyone changed their own oil and took that liability on themselves.
To the OP, you need to fight. Chances are they will try and do used engine with similar miles.
Having been an "expert" witness in a couple of these cases that have went to court, a used engine would make you "whole" and a new engine would be more than "whole" (yes when a judge said that I was like WTF)
2 years ago we had a customer bring a F150 in that had low oil pressure after getting an oil change done at Grease Monkey, in Clinton Utah (**** them). I have an email from the store manager saying fix it, take care of the customer we will pay for repairs.
When the bill was $19,000 he shit, sent it to corporate who told me to pound sand. We went to court and won $15,000, attorney cost me $7000. In the end I lost, but learned a valuable lesson.