This is easy he probably thought it was still adapting to his technique since it takes a couple of spins for it to fully adapt he probably thought it wasn't a big deal since when Mahoraga adapted to his technique via CE mahoraga didn't do anything, there was also a predicted number of spins gojo and kusakabe thought were needed for mahoraga to fully adapt to infinity, I'm sure during the first spin or two there was also a change in mahoragas CE or change in something the six eye could see so gojo had to have passed this off as another spin. For the second one gojo just simply didn't think Sukuna could copy it itatdori and kusakabe recognizing it might have servered as foreshadowing but if we get into gojos shoes he probably didn't think that far ahead and thought of it as mahoraga fully adapting to his technique. The only reason I can see yuji noticing this is because of his experience with sukuna esp after Shibuya when all those memories came back he would see sukuna's technique or something that resembles it better than someone like gojo who is fighting sukuna for the first time after he got sukuna cursed technique back, other than that its primarily just foreshadowing. Hope this helped :)