As someone on blood thinners who bruises if you just look at me, whether or not it aligns with your medical training, I can say it has and does work for me. Even my oral surgeon, a non believer, was gobsmacked at how little bruising I had following three hours of hand crushing surgery on my lower jaw.
Sometimes you need to just give something a try and learn for yourself if it works or not. For me, it has never failed. I've been using arnica in one form or another for over 25 years. Just my 2 cents worth.