I strongly disagree with that statement: I modified my Birdy (shown in the „Birdy Thread“) to excel in that exact situation. Mounting a flexible handle in the front and old inliner wheels on the rear rack it can be pulled or pushed precisely, no finesse required ;-)
The stock birdy with the lowrider front rack and its smaller wheels mounted on the rear rack used as a handle could also be pulled easily and precisely.

That said, and while I love it for urban transportation, I still think the Birdy is no substitute for a true „gravel“ type bike. It is not nearly as capable in that role as the Cannondale Slate I also own.