In WordStar it's a little more nuanced than that.

First, it's properly ^K X, as the ^K prefix subcommands block/file actions, as written by Rob Barnaby into all the WordStar versions starting with CP/M.

Second, ^KX as 'exit' means to save the latest revisions out to file before quitting, while ^KQ, 'quit', means to abandon the revisions. You might get a confirmation dialog and a chance to change your mind before you're dumped back to the commandline.

Current-convention iconic close-window behavior more closely emulates the latter.