Nix Flakes looking like the real source of the schism in the Nix community.
No. In the talks about the fork because of the real issue of MIC sponsorship there was disagreement about whether flakes should be the default among those against MIC sponsorship.
They are both issues, but the most pressing one causing large contributors to leave is the MIC sponsorship issue. The flakes/no-flakes issue existed before and wasn't causing large contributors to leave.