[anonymously]

I don’t doubt that over-vaccination is real. After puppyhood, I give nothing but the rabies as required by law, if I could avoid that too, I would after the initial 1st shot and booster.
Also, I will avoid giving the rabies vaccine to a senior or a dog with a medical condition.
Some states will consider a medical waiver, as your dog probably has, or a titer.

I hope you get some answers, by the way, SkeptVet is a real vet and tends to answer most questions even if it’s an old article. Maybe he could offer some insight?
I lost a dog to hemangiosarcoma a few years ago (no treatment options) and she had minimal vaccinations. I’ve never gotten a straight answer as to what causes this except there tends to be a genetic link and it tends to appear between ages 8-10.