Cineli carbon bars with non-cinelli stem

I have a Cinelli Neos cockpit on one of my bikes (Carbon wrapped seat post and stem + carbon monocoque bars)
I'd want to do some switching around and use the bars with a Thomson stem. However, in the Cinelli manual it says that they must only be used with a Cinelli stem.
Is this just marketing BS or can anyone suggest a genuine reason why it might be a bad idea to mix and match?

Could you quote what the manual says?
There shouldn't be any reason why any 31.8mm clamp stem wouldn't work.

Sure.
TBH it's pretty vague and doesn't make a whole lot of sense. I've since had a reply from Cinelli which is similarly vague. I've also since decided not to worry about it too much. I've now used the neos bars with a Thomson stem for a couple of rides and they haven't exploded. That's not to say they won't one day but hey ho!
The manual says:-
'We cannot guarantee the efficiency or the duration of Cinelli bars and stems assembled together with products by other manufacturers. Assembly Cinelli handlebars and stems with other brands products voids your guarantee'
The reply from Cinelli was:- We recommend to use Cinelli components because we can respond only for our own products. In any case, you can also use other components.

Just sounds like a generic liability disclaimer to me. I'd ride without worry.

You have the matching stem anyway and you just don’t want to use it? Just use it with a different stem, if it brakes and you need a warranty replacement, just say you were using the Cinelli stem that you own anyway

are the Cineli bars fake Cinelli ones?

if so, would not ride

Ha! Typo :-) Did not spot until now.
But seriously, hell no! Would not but fake anything tbh.