"Natural full body reinforcement" is not a thing. It is always over its natural physical body. Moreover, Urek could not end the fight with 25%, that was just not the case man. Both of them were not in their full power, but you only see it for Urek, assuming Luslec was at his best.
Fullbody reinforcement at 100% is the default setting of TOG as base, it's the first rookie skill we learn after harnessing shinsoo.
So Urek did in fact break it down to sub-levels, throughout this arc we never actually saw him in base.
The best that can be argued is maybe he went 100% reinforcement gainst two family heads and V at the same time of which would make massive sense considering it's three FH level beings he's facing here and not Luslec.
Also come on man, you can't even argue for Luslec here, 25% Urek factually blitzed him and coulda killed him if not for Urek literally not wanting to kill Luslec, we both saw that fight man.
We saw the limit of Luslecs physicality and reaction time, all he has left is spells that factually depend on Urek not blitzing him beforehand for him to look good.
For family heads, we did not see much of their perspective against Luslec, only one panel where Gustang complained to Urek that he brought an unwanted guest. You can't conjecture from this that Gustang could just suffocate Luslec with "pressure", if it were the case he would not care if Luslec was there or not to begin with. A FH, even without the immortality contract, can beat Luslec, but I disagree with "so incomparable power levels and stuff". I did not see anything like that, he was probably too reckless back then when he was humbled by odd-eyed snake, but currently, he seems different. Luslec can definitely be useful in fights against FH, and at least his dark charge is not to "completely disappear with a finger of an irregular", and vaam is not that powerful. And he should not be that powerful anyway, we are still in the middle, maybe even back of the things in this manhwa.
Gustang did not even give Luslec the honor of calling him by name, that's not the treatment given tp someone relevant to you.
But if Gustang though acknowledging his presence is used in the favour of Luslec what does it say about Traum blatantly flat out ignoring Luslec from beginning till the end.
I mean Traum didn't even spare him one side glace, what does this say about Luslec?
Urek acknowledging enemies far below his level always does this sorta thing, happened with Hell joe and Karaka, even Baek too.
I mean he listens to and is "scared" of Yuri for example cause she's "strong".
I guess this is my one problem with TOG, Urek making people seem much stronger or better than they are because he likes to play around leading to weird powerscaling discussions.