PLFO is not affected by voff bit (and neither by lpoff nor the still unknown bit 7, no surprise there).
LFORE = 0: LFOs are not reset on key-on or sample loop start/end. The starting position (and by that I mean the shape's phase) seems to be random, it is possible that the counter is running even if the channel is not playing anyting.
LFORE = 1: LFOs aren't working at all... quite puzzling. It looks like the period counter is forced to zero and not advancing. This does not affect the noise mode however, because period is then ignored (noise works at sampling frequency). In other words, LFORE seems to act like a disable bit. Well, the doc says it "puts the LFO in the reset state"...
Maybe I'm doing something wrong, but quite frankly there's not much room for error when all you have to do is toggle one bit. I'm going to leave this as is for now - maybe I'll figure something out later. BTW, as far as I can tell both LFOs share one common phase counter (though keep in mind ALFO can only add to attenuation while PLFO shifts frequency both up and down so it's zero point is shifted).