The Load Balancer is there because the M1 Max has two independent Neural Engines (unlike the GPU cores, which are load balanced in hardware and the OS sees as a single one even on the Ultra)... but one ANE is inexplicably disabled on all production systems. The M1 Ultra, logically, has four... and only the first in each die is enabled.
I was waiting for the Mac Studio to drop to come to a conclusion, since it's plausible one ANE could've been disabled for power reasons on the laptops... but with both secondary ANEs in each die in the M1 Ultra off, and with no reports of anyone seeing the first ANE being disabled instead (which could mean it's a yield thing), I'm going to go ahead and say there was a silicon bug or other issue that made the second ANE inoperable or problematic, and they just decided to fuse it off and leave it as dead silicon on all M1 Max/Ultra systems.
I was waiting for the Mac Studio to drop to come to a conclusion, since it's plausible one ANE could've been disabled for power reasons on the laptops... but with both secondary ANEs in each die in the M1 Ultra off, and with no reports of anyone seeing the first ANE being disabled instead (which could mean it's a yield thing), I'm going to go ahead and say there was a silicon bug or other issue that made the second ANE inoperable or problematic, and they just decided to fuse it off and leave it as dead silicon on all M1 Max/Ultra systems.