The see-saw mechanism was removed when zPiv staking was implemented; the TL;DR reason is that zPiv requires whole numbers, whereas the see-saw results in constantly varying fractions. You can read more, and view the block reward distribution, here: https://pivx.org/zpos/

You'll note that MNs are favoured over stakers for normal Piv, whereas stakers have an advantage over MNs when staking zPiv. This is in line with PIVX's overall view that stakers are the primary validators on the network, while MNs provide an additional 'bonus' level of security and facilitation.