Generative Fill / Expand - doesn't work in 32 bit mode (ie LR HDR mode)

I'm using PS 25.11 and learnt something today.
Generative Expand (when exporting images from LR Classic 13.5) won't allow you to use Generative Expand if you've used HDR mode in LR. Instead, go back to LR, make a virtual copy of the image, use the Develop module to bring it back to SD mode (so 16 bit) and then export to PS and all will work fine.

I found this because I could generatively expand some of my LR images but not others. It took a while, but I finally clicked as to the HDR issue.

I'm on Windows. I assume this is true for macOS, but can't test that.