I don't think that's super surprising though. Nvidia has deals with OpenAI as well, so not using Trainium might have as much to do with OpenAI keeping Nvidia happy, as with Trainium not being on-par.

Didn’t stop OpenAI doing a mega deal with AMD.

They just didn’t like the chips is the most logical answer. Particularly given AWS has been doing everything they can to pump up interest, and this huge PR release doesn’t even mention it at all. That omission speaks volumes.