Never understood that, either. No point in boasting about knocking this scrub out. Even Vegeta knew it wasn't a big deal.
The way Freeza mentions this, it seems like he was a bit surprised that he was able to win without transforming. I'd like to think Freeza or one of his cronies measured King Vegeta's power at some point. Or maybe Freeza was expecting him to turn into some Super Oozaru or some shit. I dunno. Just seems odd when someone like Dodoria was already capable of doing that.