I think someone already addressed it in the comments, but we do have both options, and people decides which one to use.
Going to settings and getting all to 0 gives you the slider to choose every time (it indicates that 0 disables the default percentages)
Just leaving it here in case other people in the comments is also confused about this feature.
Indeed, it works that way. "0 is disabled" doesn't say much imo, maybe there can be additional explanation that 0 allows you setting the voting power dynamically. It is just a note and would clear things greatly as myself I didn't figure it out. :)