I had migraines a couple of times in high school. I don't know what causes them, what they are, what to do to cure them, or anything else, but I do know they are horrible. A sinus headache is bad, but a migraine is a thousand times worse.
I had migraine headaches at least once a week for years. A few years ago I was prescribed a betablocker, and it helped tremendously.
Yes I get sinus headaches, and rarely migraines. Sinus headaches definitely are not migraines. It's possible that some people with migraines are getting misdiagnosed as sinus headaches, but if so, the diagnosis is really poor and I'm surprised that a doctor would come up with that.