Good stuff, I use JG in all the applications listed above but I did not know the specific lengths of the JG window and its cooldown.
It's very interesting to hear that shorter taps grant you longer windows. I assumed the window would begin after releasing G and would have the same length no matter what. Guess I should change my tapping technique.
To clarify, the cooldown is 30 frames after the first frame of hitting G? Not 30 frames after the JG active window ends?
Another useful application for JG is pushing through zoning. If you play a short range character and block a poke from a long range character, the long range character may push you right back out again or at least force you block again after you waste a lot of time running in.
However, you can shift the risk/reward in your favor by dashing in and tapping G at the timing of an immediate poke, and then dash forward after the JG ends for when they don't attack so you can up close. Guard if your JG fails and you see a delayed attack.
For example, Astaroth attacks with a 4A at tip range and you block (+0). From here, you likely can't reach him with anything to beat his backstep, especially not anything that will beat some of his followup attacks too. Choosing to attack right away to beat bullrush or another 4A or 22B can land a CH, but he could just backstep and whiff punish. Also you could guess wrong on the vertical/horizontal mixup. Moving forward can put you in range to use moves to beat these options, but moving forward wastes time. So you could run in and guard but you could get pushed out again!
So a good option here is to run in and JG. Whatever Asta throws out here is likely launch punishable on JG, and stuff that's fast enough to stop backstep-catching moves will come at a predictable i16-i20 timing. If he does nothing you'll have gained ground.
This of course doesn't beat everything but it's pretty low risk and allows you to hurt Asta real bad for something that's usually safe or requires a dangerous guess to punish hard.