Meatheadmarty if Cellebrite or other company etc found an exploit this is exactly how it could happen that we find out about.
In my opinion, the best way to find out is to have some actual evidence which seems in absence. Otherwise this is merely speculation and rumors, one can speculate endlessly and yet have no way of knowing without any form of evidence to back these claims up and getting us stuck in an endless loop without anwsers, which is pretty pointless. But indeed, perhaps one day we might find evidence of GrapheneOS being cracked, but I'm pretty sure this is not one of those moments, however it can discredit the security of GrapheneOS, some verifiable evidence would really make a difference, but I have yet to see any.