Sounds believable.
A lot of people seem to treat Rotella 15w40 like it's a magic bullet, where one size fits all.
It's not, but it does work well in a large number of popular motorcycles.
Different bikes and different applications have different needs.
Having JASO MA2 letters on the bottle is no guarantee that a specific brand or weight will meet those needs.
Not having those letters on the bottle isn't proof that a motor oil won't work well in a motorcycle either.
What's in the bottle is ultimately more important than what's written on it... But we hope there's at least a correlation!
I've tried several other more expensive motor oils in my VT750s, but in my experience, none worked as well as the Rotella T4 15w40.
That was not the case in my CB1100.
My CB1100 is running very well with T5 10w30, which does not have the JASO MA2 letters on the bottle.
Apparently, the weight of the oil is at least as important as the brand or the additive package.