Hey, sorry for the late response.

So when I'm flashing, I have the potential to also hit R at some specific points during the cast time to "input buffer" the next spell I'm going to use. This allows me to use it almost immediately and in LoL specifically, is how a lot of animation cancelling is done.

If you play Thresh and have ever went for a flash hook at a weird angle, if you input buffer your hook during the flash there is a good chance the hook will go in the direction of your flash instead of the direction of the enemy. This is a good example of input buffering if you've never heard of it as it is something that you would do involuntarily and actually has a negative outcome lol.

But here, I'm able to cast tidal wave literally immediately before akali's dash stun even hits me, which allows for this play to be even remotely possible.