[semanticist]

Not in the sense the OP means. They mean in the sense of a scientific experiment being done nominally to advance our understanding of the world (or in the case of psychology, specifically the mind and our perception of the world), vetted by a review board, and published in a peer-reviewed journal as part of the academic process.

This is very different from the colloquial use of 'experiment' to talk about an A/B test or similar. It's a very specific context where we have very specific rules in order to prevent people from committing horrendous acts in the name of obtaining greater understanding.