It's not really a grey area. You can do your oil as described earlier. This STC was written to make it more clear - because if it wasn't on this list, you'd still be in oil change limbo (even with the STC).
Side note:
Just saw this as part of an airplane ad (for a homebuilt). Tell me this doesn't sound like a propstrike:
Engine / Prop
Lyc. 0-320-150 hp, with about 300 hrs since complete overhaul but about 35hrs since rebuild with a new crank. (I chose to keep it at 150 hp because of the impending loss of Av Gas). Sensenich metal prop, approx 35hrs since new.
