I configure my Emacs to avoid splitting the frame into multiple windows -- similar to how a web browser never splits the browser window into multiple viewports. (Also my Emacs never makes a second frame.)

(The way I achieve that has changed over the years because the old way stops working.)

The way I do it now, the frame does split in some situations (e.g., when Emacs shows me a *Completions* buffer) but AFAICR I never need to manually invoke the delete-window command to get rid of the second window: it always goes away by itself.