Yes but those shortcuts are inconsistent. Cmd 1 does not bring back Messages for example. I have to press tab several times in Mail to figure out where I am in Big Sur where in Catalina the selection is always highlighted. You can’t use the keyboard to change mailboxes in Big Sur as far as I can tell. There’s no clear “language” to the shortcuts.
You’d have more usable space with Catalina on that 13” screen. It was a noticeable loss of space upgrading from Catalina to Big Sur on a 16” RMBP. I used to have space for three partially overlayed windows on my 16” screen. Now I am lucky to get two. Usable space on a 16” Big Sur MacBook is similar to a 13” Catalina MacBook. I have both. My workflows changed. There is no benefit to me as a user.
Both Messages and Mail both use Cmd+0 to bring the message viewer to the front. That's what the shortcut is listed as in the Window menu. Same with Calendar if you close the main calendar window
Messages does not have great keyboard navigation — I can't tab around like I can in Mail. I am putting this down to the fact it is a Catalyst app and they are a bit sloppy with consistency (not necessarily a Big Sur thing, as these were on Catalina)
But in Catalina Cmd-1 selects the inbox and full sidebar navigation including between accounts is possible with arrow keys. Nested lists can expand and collapse with left and right.
In Big Sur Cmd-1 just reopens the window with no selection. In addition you cannot navigate the full sidebar with arrow keys.
Combine this with the lack of visual indication of your selection and keyboard navigation becomes a struggle.
You’d have more usable space with Catalina on that 13” screen. It was a noticeable loss of space upgrading from Catalina to Big Sur on a 16” RMBP. I used to have space for three partially overlayed windows on my 16” screen. Now I am lucky to get two. Usable space on a 16” Big Sur MacBook is similar to a 13” Catalina MacBook. I have both. My workflows changed. There is no benefit to me as a user.
Take a look at this visual comparison: https://www.andrewdenty.com/blog/2020/07/01/a-visual-compari...
Look at the “traffic light” buttons. Note how much thicker the top bar is in Big Sur. It’s 50% taller! That’s a lost row of text.