At first i think it only rumour, but since a lot of people discuss it maybe it is right that ICO rating site give their ratings depends on how project pay them and not be independent. If me since first i never see ICO rating site and sometime look from it's bounty rewards.
That's it. And I would prefer to call those ratings as subjective ratings. Subjective because those ratings mostly given based on money paid to third-party rating websites, and not based on quality of projects. Such subjective ratings contain so many biases and should not be used as componental indicators to assess quality of projects.