How is it wired at the amp end though?
That would be bi-
amping (which could be done as long as you have two connections). Bi-wiring is a "stupid audiophile trick" with no real-scientific benefit.
Bi-amping (or tri-amping) can be beneficial with speakers but I doubt it helps with IEMs/headphones. I doubt multiple drivers have any benefit...
Or do you need 2 DAPs/ amps- one especially for the BA and one the DD drivers? Oh the joy!
No... Bi-wiring just uses one regular amplifier with separate wires to the woofer/tweeter. The crossover has to be built differently and the speaker (or IEM) needs separate connections for the woofer & tweeter.
Bi-amping uses two amplifiers with an active crossover in front of the amps to split the highs & lows. Most active studio monitors are bi-amplified (internally).
I have a tri-amped setup in my van. That allows me to separately-adjust the levels to the lows, mids, & highs and if I happen to clip the bass amp the other amps remain clean.