I used to run tubeless for dh sometimes, but always in dh dualplies or sometimes something like a maxxis ust minion- saved a bit of weight without compromising reliability, for me, but then I’m far from the fastest.
The thing you hear most is that at the fast end, people just end their runs with less air than they started- not so much massive deflating burps but just constant minor losses from hard corners etc. I’m not rad enough 😆 And dh world cups have been won on tubeless so it’s not hard and fast, after all it’s not like tubes never fail.
The other thing though is that I shuffled tyres more for dh and so a lot of the time I just couldn’t be assed with it. For something like the endurance downhill it seemed like a no-brainer, for day today use it sometimes felt like i was changing tyres every time I rode the thing and who can be bothered with tubeless for that? So as often as not I had middleweight tubes in
TL;DR- I liked it