> The question that remains is, does removing the {} change the output
> obtained from a command sequence in any way?
{} are used to group output from the commands into one stream.  I believe the stdout and stderr arguments to Popen allow us to get compatible behavior.  Tests need to prove that, of course.

> Which makes me wonder if getoutput/getstatusoutput should just be
> documentationally deprecated instead.  (I never use them myself, FWIW)
They were relocated from the commands module, resulting in slightly overlapping functions that don’t share a naming patter: call, check_call, getoutput, getstatusoutput.