One reason may be that the 4 cyl accord is very fuel efficient and ULEV/SULEV already plus lower cost. They probably decided to offer a "performance" hybrid with a 6 cyl similar to TCH.
Depending on the 4cyl engine you get, some of the older accords like my wife's 2001 get about 26 mpg avg, which in my opinion is kind of low for a 4 cyl.
