You're correct that VP is still reduced at the same rate as in HF19. When you cast a 100% weighted vote, it reduces your VP by 2% of your current VP. Therefore, your vote of 100% weight at 50% VP would be worth $0.50 and would only take 1% (of 100) of your VP. So you would be at 49% VP after the vote.
In other words, if you start from 50%VP and cast 100% weight votes, you can give twice as many votes that are worth half as much as if you had started casting them at 100% VP.
Does that make sense?
Yes, thats what i gigured out after posting the bounty