So IMO in the initial design, osu!mania should deal with variable BPMs by making all beats visually the same length. In the same song, speed should be higher when BPM is higher and slower when BPM is slower.Ranking Criteria wrote:
Timing changes should have a unified scroll speed by adjusting slider velocity. This is done by normalizing the scroll speed of all timing sections to the most used one in the beatmap. The number is shown in brackets after the BPM range in the song selection, e.g. BPM: 60-160 (130). Note that this guideline does not affect the ability to add slider velocity changes which are used to create SV effects.
Nowadays, a unified speed instead of unified visual length is preferred. But then, every mapper aiming for ranked are asked to go the former way by applying those workarounds. This is a bit confusing to me so I am raising the question of why should every mania map try to go this way.