actually the 250k cap is on SP held. Reducing the influence of the higher stake holders spreads the influence out to more of the community. The number of accounts held on the platform is irrelevant.
I have been watching the difference in rankings between full stake and capped stake. There is a difference and it doesn't work in any particular groups favour except as influenced by the incoming votes. The impact has moved back and forth as the votes have come in.
on SP held is also including non active accounts.