Yes, if the collar slips it reduces DoC rather than increasing it so maybe not a huge problem. At least not until the next tool makes a somewhat deeper than expected finishing cut!I made that one. It's been a while, but I think its 4140 (maybe o1?) and I think I hardened it. That was one reason I went with the 1" version was so I had a step to press the collar against. Not sure I'd trust a bolt on collar, but I have unfounded trust issues for stuff like that . I'm sure it would probably work fine if one didn't slam tools in and out and was careful with it. I'd always worry about the pullback force of the drawbar shifting my Z reference over time. It would be shifting it in the safe direction though, so not as bad but still something to watch out for.
I like the Tormach ones (https://tormach.com/tts-collar-32432.html) that are a light press fit. On the other hand they are us$24.95 plus shipping plus customs. And they also only work on a properly sized tool shank (my latest Accusize that started this thread measures 0.7499 according to my Mitutoyo mike).