I've wondered the same thing.

There is a workaround though. When an Ending is pressed i.e. A, B, C - and it is doing its thing, you can press one of the Variation buttons to 'escape' from the Ending and the Keyboard returns to the Style accompaniment mode. You can then press one of the other Endings (the one you thought you wanted when you pressed the wrong one ). There is a small delay between the pressing of a Variation and then pressing the 'appropriate' Ending button of your choice but with a little finesse it can be done in a near seamless manner. It can even add a little flair to an existing Ending - [the 'right' one of course].

Best regards,
Mike