Testimony is evidence if it is true – that is why perjury is a felony. Forensic scientists give “eyewitness testimony”, too.
You also are neglecting that the events reported in Maggie’s testimony, for instance, were public, objective and empirical, and verifiable by others. You were effectively reading a scientist’s field notebook.
You may have “objectively convinced” yourself that it is all subjective, but that doesn’t make it true.