Why doesn't the focal length of Viewport change upon zooming? As far as I know, to "zoom" means to change the focal length of a camera. But no matter how much I zoom the Viewport (not a camera in the scene) with Ctrl+MMB, the Focal Length property shown in sidebar remains "50 mm". Does Ctrl+MMB actually dolly rather than zoom? Or am I missing something?
Yes with Ctrl+MMB you don't zoom, but you dolly (by default):