In my experience bad eggs sing “I want it now” before you throw them down the garbage chute.
That guideline seems to be somewhat true in my experience: I’ve never had a new egg that floats, while older eggs are more likely to do so. Also, “middle aged” eggs will sort of float, but not burst straight to the surface. All this tells you is which ones in a mixed batch are older and should be eaten first. If an egg starts to float, it probably has weeks before it indeed goes “bad,” i.e. rotten, so in that sense it’s not a test for bad eggs. No, I’ve never gotten an actually bad one unless it was obviously cracked or something.