Mathematics & philosophy aren’t sciences because there are no hypotheses, experiments, and results; it’s just thinking and logic.
It’s still incredibly valuable and the basis of many good things.
I would also add that engineering isn’t only working with existing scientific knowledge; we were building steam trains and optimizing them long before we started doing scientific thermodynamics.
Science and math are definitely good friends and so I'm sure lots of analogies between the two could be made, but I believe the comment was getting at the epistemological difference between 'proven' (the happy state in mathematics) and 'not contradicted by experimental evidence' (the happy state in science).
It’s still incredibly valuable and the basis of many good things.
I would also add that engineering isn’t only working with existing scientific knowledge; we were building steam trains and optimizing them long before we started doing scientific thermodynamics.