When I look for white dwarf binaries (specifying WD as primary) the vast majority of the ones that show up have L Dwarf companions (though the more massive WDs have M V companions). This doesn't seem realistic. The mass ratio for main sequence primaries (e.g. K V) in SE can be a lot closer to 1, which means that one can find a K5 V orbiting a K0 V star for example. But for WDs, the mass ratio seems to be (at most) 10:1.
In fact, looking at the most massive WDs (close to 1.4 solar masses), I didn't find any companion that was even 1/10th of the mass of the white dwarf primary - though all the companions were mid-M V stars. The lower mass WDs (around 0.5 solar masses) were more like 8-10 times more massive than their invariably L brown dwarf companions, and none had M V companions.
This seems wrong. If SE uses mass ratios to generate companions then it should be using the mass of the original WD progenitor star (which would be anything between about 1 and 8 solar masses), not its current WD mass (0.5-1.44 solar mass). We should expect white dwarfs to be orbiting pretty much any kind of main sequence star or red giant, or even other WDs (maybe they are, I just don't have a way to locate systems in SE that have WD companions).
Is that what's happening here? Not sure why the mass ratio is so much more extreme for the WD companions either. In fact I think it'd be more likely for WD progenitor stars (being more massive) to have A/F/G/K V companion stars (or evolved giant versions of them) than to have M or L V ones.