Wrong in more than one way.
For starters, and those owing one can testify to this, the small keys are actually not that small. But far more important is the fact that you can easily hook it up via Midi to your e.g. BK9. Personally I like to hook it up only for the arranger section thus enabling you to play the Korg acc. section by touching the BK keyboard. Of course you can also connect the Uppers via Midi but that robs you of having four or five Upper sounds at your disposal at once: two uppers with the KMA and two or three with your main keyboard..........
As a matter of fact I have always hooked up two keyboards this way, no matter which make or size...

regards,
John