A floor is one big unit. The comparison between a tiny neck and an acre of maple is not fair. A carpenter told me that any wooden floor moves, no matter if it's oiled, painted, or lacquered. It should float, or it can be attached from one side, but it moves a lot.
I've had necks that need a tiny bit of adjusting in spring and autumn, like the original Affirma fretted 4, but not the fretless 5. My basses with carbon necks are stable round the year.