Maybe it has to do with what state you're in? We visited Dr K in Tampa several years ago & while BCBS picked up a portion of it at first they ultimately demanded their money back & we ended up paying for it all out of pocket

We even used the appeal form (or a version very similar to) in the beginning of this post.

I contacted them again today as we just found a clinic here in AZ that does the boosters & they said they still wouldn't cover any of it. Very frustrating.