Why would anyone malicious bother hiding a LPE vulnerability in a driver like this? What's the point if you're going to need another backdoor to actually get code exec in order to exploit this backdoor?
If it was obvious the Chinese government did this, then other world governments would have to respond with sanctions and import bans.
That being said, there is value in a LPE as a part of a bigger exploit chain. There's all sorts of exploits that'll give you relatively unprivileged code execution, and you'd want to silently elevate in order to make yourself persistent for instance.
Like I said, I think this is just a bug, but Windows LPEs do have value.
Then when someone says: "Huawei pwns us", they can just claim ignorance and stupidity because a small mistake here and there provides better deniability than some whitehat finding out that Huawei provides the Chinese government with the whole set of keys to the kingdom.