No, Science is a means of searching for those truths - definitely not some 'agreed upon understanding'. It's backed up by experimentation and reproducible proofs. You also make a huge bogus leap from science to humanities.
Scientific method is the process. Science itself includes the study and compendium of understandings, based on a belief system that includes shared understandings just like mathematics. The foundation of these are philosophical beliefs that we can know and understand these things. For example, on a metaphysical level, if the world around us were a simulation, then science could provide understandings about that simulated universe, but not about that which is simulating it.
This I'm afraid is rubbish. Scientific proofs categorically don't depend on philosophical beliefs. Reality is measurable and the properties measured don't care about philosophy.
But those are still approximations to the actual underlying reality. Because the other option (and yes, it's a dichotomy) is that we already defined and understood every detail of the physics that applies to our universe.
Being exact doesn't mean it is not an approximation, which was the initial topic. Being exact in science means that 2+2=4 and that can be demonstrated following a logical chain.
But that doesn't make our knowledge of the universe exact. It is still an approximation. What it can be "exact" is how we obtain and reproduce the current knowledge we have of it.