I have not responded until now, as it's been a decade since I installed a 2-pole GFCI breaker.
I had a little confusion installing that one; what I thought was a 'ground wire' on the circuit really needed to be treated as neutral, and pass through the breaker. (The receptacle was a 3-prong style).
I'd venture that if the breaker has a neutral terminal, it can handle single-pole loads. The internals appear to 'do the math.'
The only 'joker' is that the breaker likely has only one neutral connection; you'll need to combine your circuit neutrals before they get to the breaker. A pigtail and wire nut will suffice.
