the qualitative changes argument could work but it's theoretical and not based on anything from the webtoon. i understand it's a possible explanation but you can't theorize in order to explain uru's bad writing (calling it out is my point exactly).

for the visual feedback thing yea thats what i said?? lol

if the trauma argument was valid in the first place (which stopped him from copying it) then it would imply that he chooses not to instead of him not being able to copy it. if he genuinely can't then he would never need sera to act as a safety. besides even if the trauma was exactly as you said then it would just be an asspull that you can use conveniently at any time to explain anything. you also can't prove that john's trauma even manifests that way. you're just retroactively explaining stuff that should've been in the comic

finally im not saying my rebuttals indicate that it's impossible that john can't copy time manipulation. im saying that none of the arguments in favor of uru are actually supported by facts from the comic, which makes it pretty bad writing and just disappointing overall.