I think he is wrong about their supposed accomplishments in the Middle Ages. There is evidence to show they stole ideas from those they vanquished. Islam has never accomplished anything but murder and plunder.
There was Damascus steel, great for killing people. There was mobile light cavalry, great for killing people. There was also Islam, great for justifying killing people for fun and profit.
I think you are mostly right. (Thought I’m not sure ideas can be stolen — credit for originating them can be fraudulently claimed, but ideas are the common patrimony of mankind, not property.) To the extent Muslims extended human knowledge, it was mostly by making marginal, obvious, additions to what they encountered in societies they conquered. Their best claim — algebra — is basically just Greek Diophantine equations improved by the use of the Hindu concept of zero. They were just starting empirical science when their near-universal adoption of Al Ghazali’s occasionalism completely destroyed science among Muslims until they started (in violation of their religious commitments if they adhere to a fiqh that followed Al Ghazali) picking it up from the modern West in the 20th century.