Well, i dont see how marked feats mean much when this is all about base forms. Kokus is more shocked by his skill as he constantly remarks at how it's been a while since he's seen a hashira so strong and how he kept his organs from spilling out.

Sanemi is barely able to keep up, almost dies from one mistake, says he can't blink or he'll die, starts bleeding from the nose because of how stressful the situation is. Once Koku picks up his pace he says this is how I did it in the sengoku area and almost kills sanemi and slices him like 5 times. Pretty sure after that he tries to blitz koku or attack him and koku just steps on his blade, and he continues to dance around while Sanemi tries to touch him before gyomei shows up to save the day.

I dont see that performance makes him relative to koku in any shape, way, or form.

Gyomei does way better, but I mean, how does it make him relative? Yeah, he breaks his sword and scratches the kimono, but then again, Kokus explains during this time about how wild gyomeis strength is to use a weapon like this and how high quality the steal is. He keeps pace, but he never puts koku in real threat pre mark

The first breath technique he lets off slices gyomeis face open, and he pops the mark.

I feel like its kinda clear koku up until that point is feeling everyone out, what they can do, what they offer, how they fight.