ASCE 7 Table 12.2.3 says that different lateral systems in the same direction have to use the most stringent criteria between the two. One reason for why they might be doing this is because if you design the wood shearwalls for reduced forces using R=6.5, the moment frame will theoretically started to yield before the wood shearwalls hit their "design force", which is going to shift the lateral stiffness of the overall building, could induce extra torsion, etc. which could push more force to the shearwalls than what you might get from your analysis that assumes that the two systems will both be present and elastic when the design forces are reached. This may be less critical since your moment frame is likely much less stiff compared to your walls anyways, but I think it gives a sense for where they are coming from in the code.
So unfortunately, as far as I know, independent lines can't be used, except in very specific scenarios (I seem to recall something related to nonbuilding structures attached to buildings with less than 25% of the effective seismic weight, like an exterior trellis, could be designed with an independent R-value since these have cantilevered columns which would really hurt something like a plywood shearwall lateral system). This could be justification to bump your detailing up to an intermediate or special moment frame, but given that its a residence, these will come with some cost bumps of course.
Also OMF's should use R=3.5 rather than 3.25, although this was likely just a typo (Based on ASCE 7-16 anyways).
