Only last-write-wins registers use last-write-wins to resolve conflicts. Maps and Sets and Flags use an Add-Wins/Observed-Remove semantic based on fine grained causality tracking methods borrowed from dotted version vectors, counters are vectors of actor->count pairs. None of these types use temporal time at all.

For something like a single string register inside a Map (which is the register you refer to) a simple LWW seemed adequate. Maybe in future we can add some more complex type here, maybe with causal history + timestamp arbitration (like Riak's allow_mult=false.)