Who is accusing them? AKHAN Semiconductor (and the FBI), a small company in Illinois whose primary product is these diamond-coated screens. Past their founder, the second person on their about page is their "Vice President of Government Affairs;" the third person listed on their about page is their "Global Security and Intelligence Advisor," a former senior CIA officer who joined the company in May.
If the roles were reversed - a small display-tech company in China that recently got a senior Party member and intelligence officer to join made accusations about America with the help of the Chinese national police organization, and Xinhua was reporting on it - I think we would be very skeptical!
Knowing this, I personally give quite a bit of weight to any accusation against the company. I have a hard time justifying in my mind that a company operating legitimately in the US would prep their employees on how to respond during an FBI raid.
"At least two dozen times, the San Francisco headquarters locked down equipment in foreign offices to shield files from police raids."
They didn't provide any details beyond that. It's possible that the individual had just never experienced any legal compliance training, but based on their role I certainly expect they had.
It makes perfect sense to me that Huawei would prep its employees on how to deal with a raid, and being prepared for the police is not solely the action of the guilty. It tells us that Huawei is afraid of the FBI. It does not tell is that Huawei is afraid of the FBI because Huawei are bad guys.
For comparison, Corning got Gorilla Glass onto multiple companies' phones within a year of announcement in 2008. I've said before that Corning is a juggernaut in glass with a longstanding reputation, but I still don't see how those partners could agree to just buy the glass without multiple rounds of testing, and even trying to break samples, given a major selling point is durability. Huawei can't have been the only phone maker to have received AKHAN glass for testing, and it would be interesting to know what the other companies did to it before turning them down.