I'm aware that the reaction between seawater and hot ultrabasic rock generates free hydrogen during serpentinisation reactions, and your comments about some outgassing scenarios for chondritic composition being reducing enough to release free hydrogen are in the same general area.

There do seem to be ways to generate reducing atmospheres in a pre-biologic world.

The issue I was raising was that a planet would be dominantly reducing OR oxidising, but not a mixture. With time, it can change, as with the Earth becoming strongly oxidising from a formerly neutral or mild reducing condition after about 3 Ga. What it was before that is rather harder to say...