For a pure consequentialist...

Well, yes. But we're not talking about pure consequentialists. It's obvious that hybrid deontology-consequentialism is inconsistent with pure consequentialism; it's also beside the point.

Deontological constraints are seldom sufficient to determine right action. When they're not it seems perfectly natural to try to fill the neither-prohibited-nor-obligatory middle ground with something that looks pretty much like consequentialism.