These three units are overall very similar. The biggest difference is the delay time of the three pedals. The BF-2 has the longest delay time, the HF-2 the shortest (hence the more spheric, silvery sound), the BF-2B is somewhere in the middle and has some sonic overlap with the other two models.
The BF-2 uses a Panasonic MN3207 with a maximum delay time of 52.2 ms.
The BF-2B and the HF-2 both use a Panasonic MN3204 with a maximum delay time of 25.6 ms.
I just checked the schematics of the HF-2 and the BF-2B. And do you know what? They are completely identical!

So if I see it correctly BOSS marketed two identical pedals for different applications. Can it be that the sound of the HF-2 can be achieved if you adjust the trimpots (Clock) of a BF-2B?

The opamps in the Taiwanese BF-2B are from another brand, but everything else is the same. C6 is below the resonance trimpot, C7 is in the upper left.

*I still have to test how good the digital BF-3 mimicks the Bass Flanger - it did a very good job when I compared it with a Taiwanese BF-2 many years ago.