The problem with insurance policies is we never read them until we want to make a claim. I live on a river in central Texas, and flooding is not covered in my home owners policy, so I bought flood insurance from FEMA. If your policy had not purposefully discriminated against bone anchored devices, then you might be able to argue your case, but in a legal sense, they wiped their hands clean ahead of time, and you probably don't have a legal right to argue the case, because it is specifically denied in the policy...just like flood insurance.
Do you have a copy of the policy? Have you actually read the paragraph that denies bone anchored devices? The reason I ask, sometimes we can get into a personality dispute with the person on the other end of the line, and they can make it their business to make sure you have a bad day...deny your claim..."by the way a denial letter is in the mail."
Get your hands on the policy that your employer has, the one that covers you. Post the paragraph here and let's see what it says. Sometimes there is an answer written between the lines, and I am pretty good at reading what is not printed. Maybe we can find an answer. Just claiming "discrimination" is a hollow argument and will get put on permanent hold. Get the policy, and let's have a look.
James