Select All ⌘A
Selects all of the “objects” in the currently focused display. All the events. All the regions. Almost all of the channel strips.
Tracks have an entire set of selection commands, with a special case “All” menu item.
Some track operations, such as duplicating tracks or assigning tracks to a different channel strip, require that you first select the track or tracks.
Channel strips have some different behaviors as well. MIDI channel strips don’t actually contain things, they are simply parameter setting tools.
As long-time Mac user I expect ‘Select All’ to select everything. Clearly in the case of Logic Pro that expectation is unfounded. I must select carefully.