Hitscan weapons aren't supposed to combine with Volt or the M Quanta bubble's Electricity bonus, but non-hitscan (projectile) weapons are. As an example, if you normally add Toxin to a projectile weapon, then the Electricity bonus is supposed to combine with it to make Corrosive.
However, this clearly isn't working:
I have Toxin modded on my M Quanta, and the projectiles are doing mostly Electricity with the Toxin rarely procing as well. Same thing happens for Volt's shield,