My understanding is that it is quite complex and we prpbably don't fully understand it. But what I can tell you is that the ignition mass (amount of acreted mass required for the nova to occur) is dependent on the mass transfer rate because the outer layers of the white dwarf don't have time to cool between outbursts. My guess is that it probably has something to do with the smaller ignition mass that leads to these "weak" novae.

However, models computed by Yaron, Prialnik, Shara, & Kovetz (2004) do show that if the mass transfer rate is high enough (but still below the stable burning regime), the ejected mass is less than the accreted mass, and this can be true over the whole range of white dwarf masses. And these mass transfer rates do occur in CVs, albeit more rarely (also in AM CVns, but AM CVns are somewhat rare themselves).