Mirai SSJ said:
If he was talking about Current Jiren, why he'd be unsure about Jiren being stronger than Hakaishin level in the first place ? Especially when he knows Jiren was still holding back ?
Because he'd have no way of knowing exactly how much Jiren would still be holding back. He could end up not holding that much left back and just be high tier god of destruction level (on the level of the strongest gods of destruction, which are probably the ones from the four exempt universes) rather than above god of destruction level entirely.
Mirai SSJ said:
Couldn't Goku still move during Hit's Tokitobashi back in U6, which is basically ascending time itself too ? Evidence of absence isn't an evidence.
Hit's time cage is massively above any variation of timeskip.
It focuses timeskip on a single target rather than the entire surrounding area (so all that stored time energy in Hit's pocket dimension is condensed to
a single point). And judging from how Hit was planning to use it to keep Jiren frozen for the rest of the tournament we know it can be used for up to 20 minutes or more (the amount of time remaining left in the tournament) in comparison to Hit's usual timeskip which usually goes for less than a second or at most a few minutes (when Hit talked to the mob boss).
After Vados stated Jiren ascended time itself Vermoud and Marcarita talked about how Jiren was "on another level" or "in a class of his own". If breaking out of the time cage was something Vermoud easily could've done himself I don't see why they would be treating it in this way.
Heck Vermoud also seemed nervous/concerned when Jiren initially couldn't move with the time cage on him.
Ascending time means no time based technique can fully stop you for a decent amount of time. I think you would need a requisite feat to prove you are fully immune to the most powerful variation of time hax in Hit's disposal (or be so far above god of destruction level that it's a different order of magnitude. low Angel tier or higher basically).
Mirai SSJ said:
Goku was also shocked his Kamehameha didn't work on Freeza even though he didn't powered up. Same with Raditz, and several others battles in the manga. Hit's technique was so powerful that it was unbelievable to see it fail so much, even though they should have known better.
Hit's technique made Jiren struggle and grunt constantly to slowly move. Even the spirit bomb didn't make Jiren struggle to that extent.
Let's not underplay what Hit managed to accomplish with it.
Jiren even gave Hit the same respect as UI Goku after that saying at the end "the warriors i'm needed for... ...are already gone".
Jiren put forth more effort against that technique than he did against the spirit bomb (or even possibly against UI Goku considering he didn't constantly grunt or seem to heavily strain himself while fighting UI Goku). Whether or not it was his full power it was a significant portion of his power required just to slowly move. And he couldn't straight up break out of the technique until he broke the energy orb that was the source of it.