That wouldn't be what I'd say as a blanket statement...
Generally, the big advantage of having the tweeter mount off the midbass is to provide more installation options, and possibly better imaging if your factory coaxial locations are lacking.
Frequency response isn't a good example because there are quite a few component sets that can have the tweet mount coaxially in front of the midbass/midwoofer, like my Memphis Sync6's, or Boston Pro60's or Z6s. Also, components usually provide outboard crossovers that do a better job than a simple electrolytic cap on some cheap coaxials.