Wait, it goes shoot, wait time, shoot, wait time, shoot, wait time, shoot, reload. Rinse and repeat.
It has never been 4 seconds ever, but 3. It is now 3.75.
If you want them to also add a delay at the end, before he starts his reload animation, and not let this be cancelable, I am 110% down for such a change to be made, and would actually greatly enjoy it, as I don't feel Jhin is punished much at all for his relaoding, when he can just cast during it and move freely, and doesn't have to actually interrupt his damage in any meaningful way, while overcompensating for this tremendously with ludicrous multiplicative scaling beyond the already disgusting quintic scaling auto attack damage formula.