I'm just relaying what I read when they announced the TR2. Which seems to be copy-pasted to amongst the tech news sites.

Unfortunately they just state "... some first-generation X399 motherboards may not be able to deliver enough power..."

And not specifically which.

https://arstechnica.com/gadgets/2018/06/amd-unveils-threadri...

If their statement is false then that's on them.