Ratings FAQ question

Reading the help pages on ratings again, I am unsure about this statement:

only votes from regular IMDb voters are considered when creating the top 250 out of the full voting database. This explains any difference between the vote averages reported in the top 250 lists and those on the individual title pages.

Is it true that this explains any difference? What about the formula that is described as being used for the Top 250? Doesn't that make a difference?

The phrase appears here and at the bottom of the Ratings FAQ.