That the only true proletarian revolution in human history was in 1917 and then after that it was immediately corrupted and no other revolution happened ever again. They like to say they are more Leninist than Lenin, but in reality they are more Trotskyist than Trotsky.
There is no urgency among them to take any type of action, form any type of organization, support any kind of cause, and in fact doing any of that is derided and mocked.
"Ultra" is a big blanket term that usually just means any alleged "communist" who explicitly rejects all successful socialist movements as failures for one reason or another. As a result, it can seem like they have completely incoherent and contradictory beliefs because there are a lot of types of ultra. Basically anyone who declares AES as invalid or revisionist is usually an ultra, and anyone who rejects materialism in favour of idealism. Pretty much anytime someone claims to be the "one true leftist" they're an ultra.
Some Trots are, but even traditionally sharply critical trots like Cliffites (who will call AES "State Capitalism") will at least pay lip service to critical support. In practice....they're often too far on the critical and too short on the support for that to hold
That said a lot of groups traditionally considered "ultra" like Councilcoms, Left-Maoists of the "Little Deng" type, even some An Syns have supported AES while also being sharply critical. It's Mostly Bordigists and Gonzalists and individual groups that have gone to the "Bad Crazy".
Trotsky himself was kinda all over the place with praxis from opportunist to ultra in different times, and various trot orgs are often doing the same. Not always, but often.
I think some would call them that, though it depends a little bit on the individual group. I would lump most trots in with ultras personally, as they tend to do all the usual ultra things like spending more time denouncing AES than working on overthrowing capital, and trots especially seem to more frequently abandon their ideals as they get older, becoming "how I left the left" sorts of conservatives.
I once saw a thread there (highly upvoted) claiming that communists should have done revolutionary defeatist in the soviet union during ww2. They are basically lapdog of fascism with a red coat. I have seen a high number of ultras being sympathetic to fascists.
This subreddit is leftcom whereas "ultra" gets used a bit more broadly, for example Chinese communists have used it to refer to their "the cultural revolution was good actually" side of the left.