I've always considered a "Normal" lens provides the same field of view as the eye.
If you look through the viewfinder of a DSLR/SLR/EVF with both eyes open then an object will appear the same size. However most viewfinders have a magnification factor +ve or -ve so the FoV or focal length will be different, depending on that VF magnification.
Of course a "Standard" 50mm lens on the 35mm film will be a wide angle on a Medium Format camera and a short tele on a MFT camera
Unfortunately we do seem to be "stuck" with using 35mm equivalents to describe our lenses and somehow "Full Frame" has become used to describe a sensor of roughly 35mm film dimensions.
Having used half and quarter plate cameras, I still consider Full Frame to be 10"x8"