Presto, I've owned this bike for over three years and have covered seven thousand miles on it. I thoroughly serviced the bike and changed all the oils when I purchased it (it had only 3K miles on the clock). I had read and followed the advice to use ATF in the primary drive. I recently serviced the bike and changed the ATF for new. Since then, the clutch has begun to slip and drag and as I said, the ATF smells like it's been overheated.
This time I'm using a top quality bike oil (10w/40!) which is recommended for wet clutches as per advice in both of the workshop manuals I have. This afternoon I've been out on the bike and given it a very good workout, including some gentle off road work. The clutch now works much better, it's definite;y not slipping and the problems of difficult gear changes and finding neutral seem to have gone. So I'm happy about the decision.
From past experience of taking part in online forums such as this (I run a car forum) is that three things cause most controversy and the main one is which is "the only" type of oil to use, be it for a bike or a car. But as you say, personal choice rules. If I was servicing your bike and you wanted ATF (or even AFT!), that is what you'd get. If I do have problems using the oil I've used, I'll think again. After over half a century of working on all things internal combustion powered, I feel capable of making my own decisions and have often found that there is no "one size fits all" answer.