The thing is, the 4 soul child is 1, and 4 integrates towards 1, which means a relatively healthy 4 may show a lot of interest in the needs others, having more refined values which have developed beyond vague internal concepts to translate into real world applications. There is an inner moral perfectionist in the 4 (and the INFP for that matter).
I do agree that the 4 will still see this as some extension of their own identity. Instead of protecting some inner wholeness under the guise of peace-making, the 4 will actively promote an image of that wholeness in their actions. This makes 9 seems more "group friendly" over all, but 4s have slightly more of a leader side, but a lone wolf kind of leader (setting an example by striking out on their own, not leading a group). The healthier the 4, though, the more comfortable they will be within a group, as their individuality is not easily threatened.
I believe the 9 integrates towards 3, which might make them have more image awareness, so that the 9 includes their own needs into the equation more. I suppose they're on the offense a bit more to see their values realized instead of just passively mitigating to keep peace & guard the values from "profane eyes" (to quote Jung).