Just to clarify one of your points regarding Google's involvement: XLnet, and the underlying TransformerXL technology, did have Google researchers involved:
* https://ai.googleblog.com/2019/01/transformer-xl-unleashing-...
* https://arxiv.org/pdf/1901.02860.pdf
* https://arxiv.org/pdf/1906.08237.pdf
My understanding is that a CMU student interned at Google and developed most of the pieces of TransformerXL, which formed the basis of XLNet. The student and the Google researcher further collaborated with CMU researchers to finalize the work.
(For the record, I think the remainder of your points do not match my understanding of NLP, which I do research in, but I just really wanted to clarify the XLNet story a bit).