You're really missing the forest for the trees here. It's arguable which one has more theoretical exploits. This is an issue of practicality. Phones are allowed because it's normal for everyone to have one in their pocket and impractical to ban them.
With respect (I mean that in earnest), I think you may be the one missing the forest for the trees.
Nobody is arguing we should ban phones. The argument is that banning flipper zeros doesn’t accomplish anything meaningful toward security.