I see.... Well, some way to do it like Parry right before the remaining time of E is done or smth? At least it's a sure parry
Jax E does not count as a spell because it has no channel time. The only way I could handle it would be to track what buffs are on jax and when added give it a timer until it expires. Alpha has a way to track spells used through buffs being added to a hero but it has no way to callback when that buff will end currently.
Short non technical version is to support it even in a broken half working way would require a significant update to how Alpha handles spell usages. It might be something I look at in the future but given right now about 30% of the heroes in the game arent even supported yet, those are of higher priority than reworking to handle a couple spells that are going to be hit and miss regardless.
There's a lot of spells like that that are nearly impossible to handle in GOS, it's the same reason evades here 'suck' compared to internal. We dont have access to the data we need to do certain things.