By inspecting my USDA test file, I can confirm this way of instancing things works. Thank you :)
I even tested instancing using a static particles system (the old one with “Physics Type” setted to “None”, not with geometry nodes) and even if the instanced objects are not at the right place, I can see them !
But I also tested a simple “Duplicated link” (Alt+D) in Blender to share a shape between objects. And by inspecting the USDA File, I can see the mesh description twice. No instancing at all :)
Thanks for reporting this, @Francois_Grassard. I was able to reproduce and have opened an internal ticket for this bug. We will investigate this issue. We very much appreciate the feedback and testing!