Chef's are superstitious and misinformed about food science at only slightly lower rates than average, in my experience. Most of fine cooking is based on tradition and received wisdom rather than evidence.

The words "umami flavours" is a lot more palatable than MSG.

This can come from the food itself, and many recipes—in fact, almost all recipes that aren’t either fast food or molecular gastronomy—were crafted to derive umami flavours from their ingredients, rather than being “boosted” after the fact.

Which is not to say the result isn’t the same as if they just added the MSG. It’s just a different approach to adding it.

But it could refer to ingredients other than pure MSG.

Ingredients which in turn would contain glutamates, and likely monosodium glutamate.