To state what someone believes is not the same as believing it.
You wrote: “Mo-ham-head claimed the angel Gabriel spoke to him...” Based on this claim, Islam traces its origin to the God of Abraham.
I do not believe that the angel Gabriel spoke to Muhammad. Neither do I believe that Islam originated with the God of Abraham.
It is what they believe; I don’t agree with it.
Mormons claim to believe in the God of Abraham ... and believe he was once a man and became exalted to current godhood as they also can be promoted. Would you agree that they actually believe in the same God of Judaism/Christianity?