In short, I don't know - it's beyond my expertise. I'm not sure we have any way to measure boron; it's not (afaik) commonly detected in stellar atmospheres. I haven't checked the molecule lists (https://www.reddit.com/r/askscience/comments/124xb33/is_nacl_relatively_common_in_the_galaxyuniverse/je2x7n8/), but I'm not aware of any boron-containing molecules either. Your arguments sound plausible, but I'm afraid I can't weigh in on the argument.