Using wrong oil would cause engine to wear out at 200k-km instead of 400k-km. Would not cause immediate failure.
This is absolutely not true, if the deviation is small, the damage will be small, perhaps a failure after a few tens of thousands of kilometers. And if the deviation is large, the damage can appear even after a few hundreds or thousands of kilometers. Of course, it also depends on how much effort you put on the engine.
The more you challenge the engine's performance, the more important the quality of the oil increases (in relation to the engine's life and the performance you can get from it)
Motor oil is one of the cheap materials that is not recommended to save on them, and you have to be careful about the type and the quality. Our friend tells about regular use of
Motul 7100 10W 40 oil, which is a fully synthetic oil intended for use in motorcycles,
a recommended and very good oil

I bet mechanic installed oil-filtre backwards. Then realised mistake on test-drive and re-did filtre and orientation properly. But damage had already been done.
MMM... interesting claim. A most serious charge, you can't tell, so why gamble?
Take it to different mechanic for inspection.
Yes, it's a good idea to get another opinion. But before that I might want to hear what the first mechanic has to say about the problem,
since the last repair should be under his responsibility. And I add, it's a good idea to make a phone call beforehand, maybe his recommendation will be the same as mine (
get to the garage with a tow truck)?