Each rule and reg stands on it's own. If you are looking for another press release from the FAA regarding the need to register in light of Rule 107, you won't find it, as they don't need to cover that ground again. The registration is a separate rule and function. We all have access to the same info via press releases and AMA updates.

336 was drafted years before the registration process, as such the language contained in 336 would be silent on registration.