Saying Scientific Materialism is like saying Scientific Religion.
Materialism is a philosophic opinion. It is not science. It is actually a leap of faith. But people talk about it because it sounds scientific, and because it is not very obvious that it is a leap of faith.
Putting the word scientific in front of materialism does not make materialism into science any more than putting the word scientific in front of the word religion turns religion into science.
It takes more than a label or an adjective to describe what is scientific.
Philosophers refer to materialism as being “scientific materialism” because the people talking about it talk a lot about science. I use the term too. It really means “science-y sort of like one would use the word geeky. But it is just plain old materialism spoken of in science-like terminology to dress it up a bit. What would be the difference between scientific materialism and non-scientific materialism? None.
Its a bit like grape nuts. They are not grapes. They are not nuts. They are just a name. Not even a description. More of a metaphor. Grape nuts is metaphorical language, not definitive or descriptive language. Scientific materialism is metaphorical language for materialism.