Photoshop works in 8,16 or 32bit. the Export tools are 8bit afaik but if you “Save As” it will use the bit depth you’ve created in photoshop. I’ve just tested it and it works:
I’m not suggesting using it to stitch landscape tiles together as there is potential to loose quality, and get seams along the edges - but it can be a very useful tool for creating 16 and 32bit maps for other things.