it’s been this way as far as i can remember. i habitually try all different modifiers on various controls, it’s usually faster then reading the manual which is lacking sometimes.
the issue is, there’s no KC assignable to opening the GUIs of all the inserts on a channel. (there are, however, individual generic remote commands to open insert #1, insert #2, and so forth.)
there is, however, a KC to ‘close all’ plugin GUIs that are currently opened on the screen, at once. pretty handy. (ie. the same as going shift+left mouse click on any ‘e’ button in the arrange. found under “mixer > windows: close all plugins”.)