If you add the fact of repeated allegations that UNRWA allows incitement against Jews in its schoolbooks and that its telegram group of 3000 members celebrated the massacre then yeah, it's not looking good I think.
10% is a lot less than most, and that's the very broad category of "ties to militant groups", not actual Hamas members. What qualifies as a "tie"? Being related to or knowing someone in Hamas, or having to deal with them, given that they operate in Hamas territory? And "Islamist militant group" is a much broader category than just Hamas.
For example NFAC [1] is a militant group, yet it has committed negligible violence (allegedly only by ex-members, not current ones). Are they including NFAC-equivalent groups under "Islamist militants"?
[1] https://en.wikipedia.org/wiki/Not_Fucking_Around_Coalition
It seems there will be news and more details for long.
We are not talking about startups here. This is terrorism. Most probably more information will appear soon.
Any aid organization would have to be impossibly cautious in hiring in Gaza, and still they could fail such a stringent standard.