You mean a trem that is configured to dive-only.
Even on a vintage tremolo unit, if its set to float - meaning you can pull up or push down (dive) - you can't just detune your instrument.
Its not just a floyd rose issue. Even the Ibanez SAs can be made to be full floating.
And... on all trem units that can float, you can make them dive only - usually via some sort of a trem block... like grab a piece of wood and stuff it into the cavity, there you go, trem cannot pull up and you can detune to your heart's desire.