I was taught that symbiotic relationships are mutually beneficial, and is the opposite of a parasitic relationship where one benefits and the other suffers. I've never heard it used in any other way.

It's also how dictionaries define "symbiotic."

It seems like one of those things that only gets better defined if you're in the field of study, such as a biologist.

My guess is that it's a simpler word that is more memorable and 'biological' sounding. So people are more likely to remember it over mutualism

This comes from a memory of a digression during a lecture in an ecology class I was in 20yrs ago… so you know, grain of salt.

From this particular professors point of view. Symbiotic was the term to describe mutualism until recently. And then. A few papers started using symbiosis as an umbrella term for all relationships with sub-terms to describe the “benefits math”. This, to him, was annoying pedantry. But eventually all the textbooks adopted the new hierarchy of terms and the world moved on.

If you took a biology class with a text published pre-2000s, it’s very possible that your book described symbiosis as a mutually beneficial relationship between species.

Long story short: the language is fluid and ever changing, even in science fields.

So mutualistic is symbiotic. It is not wrong, just less precise.