2025 SP0 Assembly Z-up not available

The feature for Z-up assemblies does not seem to be working.

 

When I choose a new part I can make it in the Z-up orientation like so:

 

But when I try to make an assembly, the Z-up option is grayed out:

Z-up assemblies is supposed to be available in 2025 SP0.  Is this a bug I should report, or do I have something setup wrong?

 

Thanks,

Kyle