DiffWithinRangeChecker currently “implies” two other constraints: “single value”, in that it just uses the first occurrence of the other property and stops there (though no error is reported if there’s more than one value for the other property); and “item requires claim”, in that an error is reported if no value for the other property is found. On [Wikidata talk:WikiProject property constraints](https://www.wikidata.org/wiki/Wikidata_talk:WikiProject_property_constraints#difference_within_range_constraint_(Q21510854%29), @Esc3300 suggested that the second case shouldn’t happen, since the constraint reports by KrBot don’t report an error in this case.
I’m inclined to agree, since you can also explicitly put an “item requires claim” constraint on the property if that’s what you wanted… except that we now support “difference within range” on qualifiers and references (T175565), but not yet “item requires claim” (T175562). So there are cases where we don’t yet let you specify this constraint explicitly. Is that a problem?