Google is not saying have less ads per page.
They are saying if you;ve got 3 blocks of ads, 1 paragraph of content on some pages of your site, is not going to be enough.
if you've got short/thin pages, eg
forum threads with few posts.
short directory pages
product pages with short descriptions
duplicate content from other pages/sites
with 3 adsense blocks is a dead giveaway of MFA