Stated end goal of Quantum:

"The point of “becoming an attractive journal for researchers in every stage of their career” is crucial: Quantum should become an attractive publishing venue for the whole community of researchers in the field, including those who support Quantum’s vision but who, due to external constraints, cannot afford to take the risk of not publishing in a high-impact journal. Arguably this can be achieved in one of two ways: either the whole incentive system is overturned, or Quantum must become comparable to high-impact journals for the purposes of career advancement. In the short and medium term, only one of these options seems realistic. The decision to create Quantum as a selective journal is to a good extent based on the belief that it will give Quantum a much higher chance of making a difference." [source: http://quantum-journal.org/should-quantum-be-selective/]

I think it's an apples and oranges case given one (PCiX's) is a platform and the other (Q's) is a journal. It also seems to me that PCiX's goals are explicitly aligned with facilitating the sharing of results in a trust/reputation network, whereas Quantum seeks to address additional e.g career issues as well (which can limit it to more conservative decisions.)

As plainly written, that's a case of Quantum actually trying to consider real-world constraints, not a different end goal. It demonstrates seriousness.