How does this even get to 3 pages? Most of the disagreement just feels like people disagreeing because the thread was made by Azerty. Which, don't get me wrong, can be goofy a lot of the time, but completely discrediting it because of that? The thread honestly isn't even THAT badly formatted (because a lot of people also using this kind of reasoning to discredit the thread). I can understand the point being made, and I'm pretty sure anyone with basic reading comprehension can grasp the idea behind it.
Anyway, this is pretty straightforward. Infinite speed requires a character to either travel a finite distance in zero timeframe, or travel an infinite distance in finite timeframe. The important part here is the actual act of traveling a distance. X-Axis isn't really “traveling” in the first place. Technically, it's more like it is already there because it ignores distance entirely. Sure, that results in a zero-timeframe interaction, but that still isn't movement in the conventional sense required for Infinite Speed.
We literally have
Kumagawa with a very similar explanation. If it makes anyone feel better, X-Axis is basically just Spatial Hax and, at most, Conceptual shit. Same reason why
Deltarune gets Ignore Distance (a form of Spatial hax) instead of actual Infinite Speed, is because the attack itself doesn't even travel at all as it doesn't even have distance to travel into. It's. Already. There. It cuts the distance, it deliberately ignore it, of course it's gonna be instantaneous.