Ah, so you haven't purchased it yet? That's good, since you can still choose something different if it turns out that the FP-30 doesn't meet your needs and wants!
Regarding my interpretation of the manual and MIDI guide, the fact that the manual specifically mentions the damper pedal's action with respect to Twin Piano mode, but not with respect to Split mode, makes me think that the pedal acts differently in Twin Piano mode than in Split mode. And the fact that the MIDI guide says the "Rx." switches for the various channels are turned on by default seems to confirm that the pedal does affect the left-hand voice.
I agree that having to go the MIDI route would be more work, and would be very inconvenient if you wanted to use the FP-30 in gigs but don't want to carry around a tablet or laptop or computer to connect the FP-30 to. On the other hand, if you're going to keep it set up in one spot at home then it might not be too inconvenient, especially if you intend to use the FP-30 with a DAW to record your performances or play virtual instruments, in which case you'd want to have it connected to a computer anyway.
If you need help setting up the MIDI commands, that's no problem-- I or someone else could help with it. But it would definitely be simpler to just buy an instrument that meets your particular needs and wants.