PoE 2 Inconsistent attack speed when holding/spamming key

I'm using Storm Wave with Martial Tempo support bound on Q. The skill (at least visually) seems to attack faster when I'm spamming the button instead of holding.

I've encountered this as well. Using WASD movement.
On my Ranger every once in awhile I could get double attack speed (or something like that). It even reloaded much much faster.

My buddy could reproduce this on his Monk using Storm Wave.
He's using mouse movement.

How he did it:
1. Give a single mouse movement input (click to move)
2. It's important the character is moving
3. SPAM the ability key. He was using W in this example
4. Observe a MUCH faster attack speed