FWIW, I agree that this isn't a bug, at least in terms of Jumper physics.
However, there's a different angle to look at this one, as Simon alluded to: the splat pad is the source of the bug here, not the Jumper.
A case could be made for in-game gravity requiring splat pad interaction, and that would include the descent phase of Jumper and Reacher (and any other gravity-affected movement). I’d also then want to look at whether a splat pad should respond to upwards force as well (e.g. the ascent phase of Jumper and Reacher), making both positive and negative Gs a factor.
I suggest that it should either be left as-is or “fixed” only alongside these considerations, and certainly not in isolation as a Jumper bug.