Yeah. My choice of vocabulary wasn't perfect I agree. No need to discuss such a petty thing
I suppose the "one handers not being able to use with a shield" is not for the realism sake. It is to make some onehander weapons unique to the swashbuckler class, to be able to give them identical stats to 2handers.
I think, the effects of having a free left arm must have an influence. That is the only buff the swashbuckler class deserves. Being able to punch could have been nice for instance.
Besides, it could have been better if some one handed weapons could get a secondary mode like "without a shield". Instead of a couple of different swords that can't be used with shields.