Emacs on Mac file opening buffer switching behaviour

I am a very happy user of Emacs on Linux, and a far less happy one on Mac. I can't seem to get one thing right: switching buffers - I can't fathom the behaviour of Emacs on Mac with

-x b

. Looks like it rotates through a number of windows rather than being back-and-forth between two buffers like on Linux. Emacs 28.1 (9.0) on Sonoma