Slider Velocity

Why is it, that in Mania the game doesn't speed up when there are green sections, while on Mania specific maps, it does.
Also it does change speed in Taiko, so why not in mania?
I recall seeing a video of Mania some long time ago in which score was completely screwed up, but SV takes part at the speed.
Since this wouldn't make things easier or harder (maybe harder, but those mods still give 1.00) I'd say make it a mod (or just a little checkmark when playing it, just like the Disable Video/Storyboard, BG Dim etc.
Otherwise it can also be an unranked mod, but I really want it
Oh, this ofcourse only counts for auto-converts, which are my favorite