I dont know how you come to the conclusion they are not relative, weve seen people that werent realtive multiple times and that fight was not it. Gin vs hiyori, yama vs ayon, ichigo vs shaz, kenpachi vs ichigo start of fight, etc. Ichigo blocks ulqs first attack, dodged his 2nd, blocked his third, and then uses a getsuga which is blocked. Ulq then uses cero osc which makes him 10x stronger. and CANNOT one shot ichigo. Bro ichigos bankai amps his speed not durability. Funny as well since ulq isnt even much faster than ichigo. He uses sonido to overtake him, 1st scene sonido, throws lance showing not much faster, runs up ichigo blocks, they then do respective blast and they react to both.
We legit see someone that is not relative earlier in the fight. Base ulq and masked ichigo, ulq tries to block his attack with his sword, sword cracks.
pre grim fight ichigo vs ulq, puts mask on and uses a getsuga to block ulqs cero nigh one shot.
yes ulq doing this is to introduce ichigo to a black cero, which when it is actually used in comparison its named. And when others variates are used they are also name so ulq doing this is only to say it is like a cero and we have a back cero. ulq says that and then proceeds to say "no matter how similar your appearance or techniques may be to an arrancars they're as different as heaven and hell." "its understandable that humans and soul reapers would mimic arrancar to increase their powre but you will never be out equals." So getsuga is copying ceros but is weaker than it by a large margin, we actually see it against a regular cero and it does loose. In grim vs ichigo final fight in base, it can still contest it but its not as close as ulq and fh ichigo.
ulqs res powers dont matter (arbitrary relative numbers)
ichigo in base - 80
ulq in base - 100
ichigo with mask - 800
ulq in res- 1000
ichigo with getsuga mask - 900 (still loses to ulqs lance twice)
ulq with cero osc- 10,000