ninja edit: jumpsquat affects wavedashing cause you want to air dodge on your first airborne frame. That means for Fox you air dodge on frame four, and for Falco you air dodge on frame five. its a 1/30th of a second difference which just takes getting used to.
To clarify why this is, your inputs are applied on the frame after they are read by the game, often referred to as 'frame 0' or the 'input frame' vs 'frame 1'. So the first possible frame that you can input an action for Falco during his jumpsquat is the frame before he is airborne (frame 5), and since the airdodge animation instantly changes your speed regardless of what it was (the magnitude is the same for all characters but the direction is based on your analog stick position), and since speed is applied to your characters position on the same frame (which makes it a backward difference from a mathematics perspective), during a frame perfect wavedash you never leave the ground, and a frame perfect wavedash with the same angle will always move you the same distance (after the jumpsquat).
All of that aside, if you watch Fox VODs, even up to high level play, a lot of players don't get or use frame perfect wavedashes during movement in neutral (this is to differentiate from the wavedashes during waveshine combos, the tight timing requirements of which seems to cause players to optimize their wavedash inputs), which suggests as a general observation that wavedashing feels easier with fox because people airdodge anywhere from frame 3 of his jumpsquat through to 1-2 jump frames. That is to say, during movement in the neutral, most fox players that I've observed give themselves a 2-4 frame window to wavedash, which would be correspond in time (and therefore muscle memory) to frame 3 of falco's wavedash on. As a result of this muscle memory, players likely feel that Falco is harder or 'weirder' to wavedash since half of the frames (frames 3 and 4 of the jumpsquat) they would have conditioned themselves to airdodge in are now completely unactionable, leaning towards 2/3ds to all of them being unactionable if they gave themselves a 3 or 2 frame window, respectively.
PS note: If you use the in-game debug mode to look at Falco's frame data with the animation states up (either with 20XX, AR codes, Dolphin, etc), the jumpsquat animation is indexed from 0 (like arrays in C-like languages), so if you're breaking down falco's wd frame by frame, the in-game display displays the animation frame of the Jumpsquat as: (0,1,2,3,4) where 4 is your first actionable input frame (which would be referred to you by people as 'frame 5 of his jumpsquat'). This aspect of the game unfortunately results in some confusion since 'frame 0' is referred to as the input frame for techniques or actions by the community when discussing frame data, but the game (inconsistently) uses 0-indexing for animations when displaying information about their state.
Edit: changed "after the end of jumpsquat" to "after the jumpsquat" to be less ambiguous