Good read. To answer the question in the title. No. One failed test resulting a team penalty would be harsh and not, as Wenger says, acceptance of such usage.(He seems to be finding a lot to complain about this days) It could be a mistake, inadvertent etc. Yes, it should really never happen if players just check with trainers but it could happen. And yes, a fat burner could help increase physical performance, however minute, so I don’t think its unfair to include that.