Well, I think about it like this... if LSDJ processes in ticks, a HF VIB shape would have a smooth wave over those ticks, but a spread out wave would be slowed down, yeah?
Like, if _--==--_--==--_--==--_--==--_--==--_ is HF, then _____-----------=========-----------________ is the larger sine wave over the same number of ticks, which leads to slower vibrato.
Extra shapes are just the icing on top, but they work the same way, yeah?
Like, the square is _______________================_______________ over the same number of ticks, and
the sawtooth is ___----=====_____-----=====___----=====_____-----===== over the same number of ticks. Which is why you get different pulse sweeps and bends using different waves. You can hear it real good on a square, the vibrato just bounces back and forth between your chosen tones.
Did that make sense? Hm, I wonder. Also, sorry if this was common knowledge.