I am sorry that both of your parents may have it. It isn't easy to deal with at all. I think combativeness is an early symptom and goes away as other problems arise. That was how it went with my Mom. Personality may be a factor in how argumentative/combative a person with dementia is too. Thankfully Mom is as sweet as can be (always has been) and she is too frail to be a physical problem for me.
I wish you the best in helping them. It may well be the biggest challenge you have ever undertaken.
I don’t remember hearing that at all!