Well but this is just the thing. Some people would absolutely disagree and say that if they have the same bass FR, they won't have different bass response. But others would not! It's one of the most heated disagreements in headphonedom.

Here are my two points:

First, as I said, it's not always so much how much louder the bass is as a whole as how smoothly it transitions into the mids. And this can affect the character of the bass a lot. Second, if you're looking for "fast" bass, that can boil down to treble response too. Bass instruments will have higher harmonics that are affected by higher frequencies, and these can also affect the impression of what sounds clean or not—whether these higher harmonics are rendered accurately.

But I would probably have to try a good planar headphone before I could authoritatively say of myself "no it's just FR but more nuanced" or "there actually is a je ne sais quoi to the bass texturing."