This is more or less what I'd always assumed (that they do consider that healers can and often will DPS, but that it isn't a criterion for tuning clear minimums).

Nice to know, but I don't think this will make a difference in anyone's play style. Players who see healer DPS as a crutch for groups with poor DPS will continue to act as if attacking mobs were beneath them/not in their job description, while better-rounded/more active players will keep doing what they're doing. And the truly bad players will keep on killing everyone regardless of how they play, but that too is status quo.