Command clicking to override the grid does usually work though. I'm in the habit of sometimes pressing and holding command before clicking with the Smart tool to override the grid and I'm not sure if this triggers the weirdness or at least makes it happen more often. This seems to happen more when zoomed into a small number bars. If I then click the same region again with the Selector tool the whole Edit window gets selected again. If I change to the Grabber tool then just the region I click on gets selected. Then, wherever I click in the session with the Selector tool or upper half of a playlist with the Smart Tool, everything remains selected rather than simply placing the cursor.
If I switch to the Selector tool it still happens. Sometimes when I'm doing this everything in the Edit window gets selected.
I'm clicking in the top half of a region with the Smart Tool (so the i beam appears) to place the cursor.