Sometimes Alt+Click layer shows only that layer or shows all layers and sometimes it only shows and hides that layer. It's repeatable, but not predictable (seems intermittent). Version 2021.92 on Windows 10, 64-bit.
This is an old sneaker I scanned using my camera and some FOSS software called Visual SFM plus Meshlab. The scan came out a little lump so it was cleaned up and some details added in 3DC.
Here is a turntable.
http://bit.ly/1tieyvT