If you don't complete activities to hurt your power, then you're playing PP, and you care about the result.
Those that complete activities without a thought about their power are unintentional 5cers.
You can't have it both ways. Either you care about the result or you don't, and if you don't, Sandro's trying to tone you down, if you do, you're a PvPer, supporting your power against other players trying to undermine it.
But, playing anywhere other than open has no bearing on 5c'ing. Carrying on certain activities beyond their benefit to the power is not exclusive to Solo. Adding an influence modifier to opens activities has no bearing on 5c activities. Sandro is looking at ways to minimize the effects of 5c activity. Coolness. He also, in the same post, mentioned an unrelated (to 5th column stuff) idea to subsidize open PP. They are not linked issues.