I agree with that.
The problem is - as I have found - that you can have two pages with same design - same menu structure - very similar metatags - but different articles . One will be OK - one will be in -950
The problem is as annej says
and this is compounded when you add in a potential IBL factor - so you may correctly change all the words in an article only to have no improvement as for that page it is not a "phrase" problem but the lack of a couple of IBL.