That's absolutely how I'd define reality, it is what is left when people take away their assumptions, assertions and claims. It's what actually exists beyond human perception. I don't think it's at all philosophical.
Like I said, it is not my intent to derail this thread into a discussion of the nature of reality - which is, regardless of what you think, a subject of philosophical debate to this day. Specifically, it's the central focus of ontology. You're making an assumption, assertion, and claim about the nature of reality whether you recognize it or not, and that's quite philosophical.
I never know which ontological framework a person is operating from when they say that word "reality." If a person is deriving knowledge from reality, which reality or parts of reality are they talking about? It's a relevant question, and I think it is a good idea for people who say "I derive knowledge from reality" to clarify what they mean by that.