Why tubeless tires without tubeless approval

Question

There are tubless ready tires out there (as the Chinook Pass) that are not approved for tubeless use but still have the label "tubeless ready"

For this specific tire I found that out since I was looking for a 28 tube for my Zipp 303s and only tubeless ready tires are allowed since hookless. And in the list of approved tires you can find the Chinook Pass.

I am just wondering why tires, where the producer says it should not be used tubeless, can still be tubeless-ready?

Edit:

"Where specifically does the producer say that they are not approved for tubeless use? I did not find such a claim in the links provided."

RH is talking only about the Stampede in the cited passage below but that counts also for the Chinook (I could not find a direct confirmation for this only indirectly you could infer to it since they only describe a tuble installation on their webside) they told me that via mail a while a ago though.

What about tubeless installations of tires that aren’t tubeless-compatible?

Maybe you’ve seen Ted King run Stampede Pass 700C x 32 tubeless. It’s doable, and can be safe if you know what you are doing. Officially, we cannot recommend it, and you are on your own if something goes wrong. Make sure not to exceed 60 psi with any tubeless installation.[1]

Answer 1

Tubeless vs. Tubeless-Ready

Tubeless is the older designation and in simple terms, represents tires that were air-tight in all aspects, including the sidewalls. This resulted in tires with stiffer, less supple sidewalls but could be used without sealant, at least in theory.

Tubeless-Ready has become more prominent, and are just as capable of being run tubeless as “Tubeless” tires are. The main difference is a more supple, usually thinner, and possibly porous sidewall, which is sealed by the use of sealant in the tire. The more supple sidewalls typically make the tire lighter, but are also slightly more vulnerable to cuts.

I asked (and answered) this question myself a couple years ago when my go-to tires stopped being labeled “Tubeless” and were only available as a “Tubeless-ready” product.