I don't think that's true. You can sign up using your Instagram account, but I don't think it happens automatically. Instagram has 1.4B active users for reference.

What makes you think the shadow accounts are part of the 100M figure? The Android app alone is already in the 50M+ downloads band.

Very nice! What were your motivations for the reduced build height?

I use the RealThunder branch of FreeCAD because I didn't like the boiling-the-frog changes that were being made to the free tier of Fusion 360. It is already good enough for my needs, and new features are getting added frequently, e.g. an offset tool for sketches and the ability to select regions on faces to extrude.