Steps 4 an 5 refer to settings dictionaries as if they were IDL dictionaries, having members. But settings dictionaries are not IDL dictionaries and their internal structure understood to be an implementation detail elsewhere in the spec.

The spec explicitly says We use the term settings dictionary for the set of values that might be applied as settings to the object., which does not necessarily translate to they working like IDL dictionaries with explicit members that might or might not be present.

Another problem is that step 4 says If constraintValue is a boolean, but the constrainable property is not, which sounds impossible in IDL. I understand that this is intended to support pan/tilt/zoom constraints which accept boolean and numeric values. These constraints are of type (boolean or ConstraintDouble), so the constraint value is compatible with the property. One way to make this clearer is to treat this particular constraint type separately, just like purely numeric constraints are treated separately from purely boolean/enum/string constraints.