Exporting directly from WorldMachine Pro as a tiled option works perfectly. Thank you! I wasn’t aware that world machine exported r16 directly, and was also unfamiliar with the tiling functionality.
For future reference, I found this doc after the fact and covers the process well:
For other users who may encounter this issue … a naive export of height using something like photoshop will not work for tiled world composition landscapes - use world machine pro!