Especially when some other outlet reports "Scientific American says XYZ". Readers will absolutely treat this as if there are scientific underpinnings. They will give it more credence than a regular opinion piece. The vast majority of them will never know it was even an opinion piece in the first place.

I would guess that if you asked 100 random people who had heard of Scientific American, many/most would say that SA publishes science and has no Opinion section. Before this dustup, I would have been in that camp.