I don't really know what
valid means here. I also don't know how you see
rules being related to
mechanical structure, nor how you see either/both of these being related to
teeth.
My view is that if the GM is free from moment to moment of adjudication to decide what happens in the fiction, and if the rules of the game place no significant constraint on that, then there are no
teeth. Declaring an action may prompt a check, or may not. Failing at any such check may bring down disaster, or may not. Succeeding at it may avert disaster, or may not.
I'm not really seeing much in the way of
rules either. Being trained in a skill, or with a tool, puts a "tag" on my PC sheet which says
I'm a bit better at this than I otherwise would be. But there is no rule that states when that tag actually matters to resolution. The GM is welcome to have regard to it, or not.
This is a wildly different way to approach RPGing from BitD. And (to restate what I think is
@Ovinomancer's point) it provides support only in the sense that it establishes those tags on PC sheets and gives the GM the permissions I've described above.
I think the contrast with how D&D approaches combat - where there are teeth, and there is much more to resolution than just a few tags and some GM permissions - is pretty striking. Likewise the contrast with how classic D&D (AD&D, B/X) approaches dungeon exploration - where again there are teeth, in the form of concrete rules about how much time passes while doing various things that in turn interface with spell durations, wandering monsters tables (that interact with dungeon level, which in turn interacts with treasure available) and the like.
If someone said that Prince Valiant provides support for D&D-esque dungeoneering because it has machinery for framing and resolving perception checks and dodging scything blades, I think the reply would be pretty obvious: while those things are true, it has no machinery for giving the whole process of exploration
teeth. The GM can dial up or dial down the pressure at will, and the passage of time means nothing besides colour.
Somewhat the same thing is true of the "heist" I described upthread from my Traveller game. My narration of an approaching Imperial Navy cutter was a "soft move" (in PbtA) terms, in that it introduced an approaching threat/problem; and it allowed me to colour some subsequent narration of the passage of time and the resolution of actions on board the alien vessel, much as a PbtA GM might. But it had no
teeth in that, until I narrated its arrival, it was just a source of narrative colour. I think a system that has a way to make that sort of thing more than just colour - like a
clock framework - is clearly providing more support for heist/caper RPGing.