I mean, if you can believe that a wall supporting nothing with nothing above it and nothing below the floor to support it is somehow structural, and want to pay someone to tell you otherwise, be my guest. I just know there’s a point where one can be far-more-than-reasonably sure of a thing and not need to spend money to validate the 0.001% probability.

My office wall is not structural, and I am fully sure without the aid of an engineer. The rafters run parallel to the wall. From the attic I can see the whole top of the plate, the drywall of the ceilings on each side, and the short boards (can’t think of the name) tying the header to the rafters.

There are times where one can absolutely tell without a structural engineer.