They use caiziyou, AKA roasted rapeseed oil, which has a high level of erucic acid, similar to mustard oil. (Rapeseed is a member of the mustard family. Canola is low-erucic acid rapeseed oil.)
Rapeseed oil for cooking is a staple in Germany.
If erucic acid or its thermal products are the cause, there would also be many cases of lung cancer in Germany.
I think this is a naming thing, canola is an English word for a variety of rapeseed, and IIUC Germany uses the same food-safe version.