The people that throw around that assumption just have no clue how the games industry works, especially when they have no knowledge of how the times reviewers have been paid off has dramatically blown up in the faces of the companies paying in the first place, read up on driver 3 or kane and lynch to see why this type of shit was not only rare back then but has since become even more impossible to do, this kind of shit simply can't be kept under wraps to put it lightly. Now there are some shady things around trying to appease publishers so they still get future review copies, but that topic is far more nuanced and variable than people who would throw the accusation around to even bother reading up on, and even that has also been cracked down on immensely.
For kojima specifically its laughable, cause like why the hell would the guy be paying off people to review his game nicely then not bother to get good scores from the biggest site in the industry ign.