Selective friction guards against a specific way protection goes wrong: smoothing away all resistance in the name of convenience. The framework distinguishes two kinds. Wasteful friction — pointless bureaucracy, arbitrary obstacles — should be removed, and removing it is a real service. Developmental friction — the struggle that builds a skill, the negotiation that builds a relationship, the uncertainty that trains judgment, the responsibility that produces maturity — is doing work, and removing it quietly hollows the participant. So the maxim is remove waste, not all resistance, because the two are not the same thing.
It is the protector-scenario companion of friction proportionality (difficulty matched to consequence) and of the framework’s stance against frictionless design: the goal was never less friction but no wasted friction — and, here, no missing friction where struggle is how a capacity is formed. A protected failure space is largely a place where developmental friction is deliberately preserved.