That is true. I've seen that where people try skinning a wooden object with one layer of cf to "make it stronger". That sort of thing shows a misunderstanding of how the material works.
I have also seen plenty of examples where people misinterpret or misunderstand things like the Young's modulus when comparing two materials. They see a chart showing that one is higher or lower for strength or stiffness and use it to choose their material.
It is important to understand that critical part design is far more complicated than any one piece of data. Strength and stiffness is affected by part shape, part design, wall thickness, the manufacturing process, choice of resin etc.... as well as choice of material.
If you ask most people here, "what is stiffer, a steel or an aluminum cnc machine frame?", most would answer "steel". But, what if the steel frame had a 1/4" wall thickness and the aluminum had 1" walls? What if one used plates and the other square tubes?There are at least as many complexities with composites. With a well made composite, there is synergy between multiple materials. A poorly designed ones could easily see one material drag the other down.