I always told people hash's i-frame has a tiny gap at the start of the animation but no one really believed me so I made proof. The gap gets wider when using Flow: Sand Warp from pre-awakening. Thought the dummy would be a good place to show it since it isn't as latency-reliant as players and it is much more reproducible and has no animation acceleration. I heavily advocate you do the same thing for your class's "seamless" animations with no gap and show the devs their wonderful work.
Sorry for the low quality: