There’s no problem with the routing itself; everything is known for all latencies when the L2P mapping is done. The problem is in the physical realization of that routing in minimal time. A one-level tree would have so many sources that we’d need another pipe cycle in there to keep the clock rate up.
So, to clarify: the problem is not that the routing information isn’t known far enough in advance, but that the results for the one-cycle latency ops don’t exist that far in advance? And anything specified as latency 2 or more will exist a full cycle in advance?