If you use an item or ability during the punch part of a charged punch, it continues your momentum.

[daniel_81620]

Any ability or item you use during the punch part of a heavy punch, continues your momentum at the time of the item/ability use, instead of decelerating. . (replicated with paradox 3, fleetfoot, other items I forget)

https://imgur.com/a/zrz1sF2

Also believe a similar thing is happening when Vindicta uses her fly, and as she is rising up, uses fleet footwork to preserve her momentum and fly fast.