Having trained with some weapons in my younger days as a martial arts assistant instructor, I would submit that when I trained with two weapons (nunchucks, sais) I also improved my use of single weapons of the same type.
As far as foot soldiers training with two handed weapons, yes pole arms and spears were common, but they were trained as a unit fighting in formation, not single combat. Thus the expertise necessary to use weapons like great axe or great sword (in DDO martial weapons vs simple weapons).
I just don't see the need or purpose of this whole endeavor. First we are taking what is the common style of fighting and making it "special", secondly it does not fit thematically as a bard, thirdly what the heck is "Swashbuckler" doing as a PrE anyway? To me we could just as easily now make things like Adventurer, Explorer, Bodyguard, Scout, Soldier, and Bandit. It's more of a profession filled by other classes/PrE's rather than a PrE unto itself. Most all other PrE's focus on a fighting style within a class.
I don't know, maybe if the name was something other than swashbuckler, and if it wasn't a bard PrE, it would be okay. I still don't think single weapon fighting should be equal with the other styles though.
Just my opinion, and I see I am in the minority. I guess everyone is excited about something "new". I'd rather they worked on improving some of the cool PrE's that just don't work, like EK. *shrug*