Are you really trying to both sides this? Firstly the law in question uses the word "risk", not "certainty" so I'm sure the ICJ ruling that there's a plausible case of genocide against Israel fits that description.

Secondly, the Western nations that cut funding from the UNRWA did so as a form of protest after Israel lost in court and as a way to de-legitimise the case against Israel, as a lot of findings in the preliminary ruling of the ICJ use UN figures as a source. They are not cutting funding from the UNRWA because they believe in Israel's "dossier of evidence" with regards to UNRWA participation in October 7, no one believes that, they are cutting funding from the UNRWA to tarnish the reputation of the ICJ, the UN and to attempt to tarnish the evidence used in the case of genocide against Israel. Because if Israel is found guilty of genocide, these nations will be complicit in that genocide. So they are simultaneously trying to cover their arses and reduce the chances of that happening through cutting funding from the UNRWA, for the reasons mentioned above.