I assume you mean Kelade's video, in which case
you've got to be joking. The kid is a hack who got his youtube following for
plagiarizing my guides, and his "content" has taken a sharp nosedive ever since he was called out on it. I don't want to beat a dead horse, but I will point out that his T21 sims are
completely wrong, with the majority of the trinkets not even being used (given that they're not actually implemented in the currently public versions of SimC, I should be an update within the next week to fix that), so
the trinkets in his bar graphs aren't actually dealing any damage - that's why you see such a slight increase over no-trinket, because the sim is only evaluating the stat change without any effect!
I'd also point out that a very similar video was made for T20, which said that Cinders and Engine of Eradication were going to be the top two trinkets for Fury, based off woefully inaccurate testing (read: smacking a dummy for about 2m with similarly broken simulations to back up the erroneous claims), and when asked in relation to my findings that Moonglavies was an "AoE only" trinket, a position which wasn't reversed until a good three weeks after the tier released. So... good luck with that source.
Anyway, 860 Arcano is not better than most trinkets at 930, and certainly not better than the ones Fury prioritizes. I'll grant that it is better than a lot of trinkets, but not at that pronounced of an ilvl difference, and getting one at a competitive ilevel is progressively harder as ilevel increases. At any rate, I don't think you'll find anyone argue that Arcanocrystal is in any way balanced or a well-designed trinket; it should have been taken out back and shot ages ago for all the contention it causes.
Lastly, I wouldn't worry about CoF right now; there's still a lot of iteration to be done, especially once the raid tuning happens (as in every tier). Also, Forgefiend's Fabricator (Fire Mines) is sleeper OP right now; it's a bit tricky to use, but if you want a strong on-use trinket in Antorus, that's it.