Edit: I misinterpreted the screenshot as I didn't see that doctor profiler setup thing initially. That might make my point here moot:
Can you clarify what you see as a memory leak here? I only see increased memory usage which is not a leak and could be perfectly explained by the fact that in one case you create hundreds (thousands?) of computed properties while in the other you simply don't.
A leak would be if you destroyed all of these Posts again and memory usage would not decrease to the same level.