While it is unreleased, they both fit basically the same role with the same typing. I can see why we're making the parallels here, but Kyurem-Black is actually superior to Bax. Better overall stats (115/145/92/75/86/86 vs 125/170/100/120/90/95), can actually make very good use of a Mixed set, doesn't debilitate itself with a No Miss + Double Damage debuff, has its own 120 BP STAB move (Outrage), and actually has more reliable Ice STAB plus a better overall move pool. It also isn't mostly reliant on Choice Band or Dragon Dance.
The point is more that Kyurem-B is not indicated by anything to be coming into the game at such a point where it is relevant beyond a point of reference from previous meta games.
With that said from that angle, I disagree with at least half of the points you are making in favor of Kyu-B in this particular post, primarily in regards to the move discussion and item reliance. Would also cite that Bax's immunity to burns is a massive Boon on a Physical attacker
There is no scenario under which I would consider Outrage superior to Glaive Rush as a Physical Dragon STAB, because Outrage locking you in yields a much worse drawback in the event it works, since Kyurem is forced into the move multiple times even without concerns for Confusion. Bax's extra damage taken only persists until its next action (which STAB Ice Shard could help circumvent without totally forfeiting momentum), while retaining the ability to switch-out or attack with another move to avoid limiting responses any more than necessary. Outrage even when it works will leave you stuck throwing the same move out, making the response significantly easier and exploitable on Band/AoA sets, while Dragon Claw incurs a drop in power that keeps Bax decently ahead on comparable items.
252 Atk Baxcalibur Glaive Rush vs. 248 HP / 0 Def Mew: 213-252 (52.8 - 62.5%) -- guaranteed 2HKO
252 Atk Teravolt Kyurem-Black Dragon Claw vs. 248 HP / 0 Def Mew: 160-190 (39.7 - 47.1%) -- guaranteed 3HKO
Reliable Ice STAB is moot, with Kyu-B only possessing Icicle Spear for reliable Physical STAB, a move Bax also has access to if you don't want Icicle Crash (the move most prescribed for Kyu-B before anyway) and in fact seems to run as a rogue option with Loaded Dice in some teams.
Kyurem-B's movepool is only particularly better than Bax if running mixed sets. Physically they both are going to run into some mild obstacle with limited move options (Kyurem needs EP Mixed to hit Steels compared to Bax EQ, while Bax lacks SE Fusion Bolt Coverage for stuff like Corviknight or particularly fat Waters).
Lack of mixed sets, a worse speed, and marginally lower Bulk are fair points but the others are not particularly strong points when making the comparison, nor do they forward the discussion when people are focusing on Bax as a 1-2 trick pony whose 1-2 tricks is extremely hard wallbreaking anyway rather than seeking variety.