I think that makes his lineage fail the test of solidity.
Why do you think so?
To my experience and my understanding of "etiquette" it is natural, that the lineage of a teacher is displayed by himself in face to face conversation. And only by himself.
I have more than once experienced that a lineage that was to read or was told even by advanced studends differed from what the teacher himself said, when asked. And in some cases it was kind of complicated, not so one-dimensional even when directly talking about it.
This is another aspect (comparison of fees; demanding some "video-proof" without practicing with the teacher concerned; discussion of lineage without talking directly to the concerned teacher) that I have never experienced being discussed regarding another teacher. Why is this so? I don't understand that.