That might make you feel all fuzzy and satisfied, but the issue is not nearly as straightforward as that, anyway. Do you have chilled microbolometers with 1-photon sensitivity to ensure absolute darkness? Do you even know how much darkness is "dark enough" to be safe for your film, even if you did? Most people measure the darkness of a darkroom by how dark it "looks" in there. That's only a very rough measurement. You have to use both your eyes and your brain when determining appropriate light-tightness.It either is, or is not. There is no try...
The fundamental error in reasoning here is that if it's black to your eyes, it's black to the film. But that's a very simplistic criteria. You can actually develop film by inspection by shining enough light on it that you can see it with your eyes, but the film is unaffected. So much for visible=bad. You can easily see a lit candle from across a completely dark basketball court, but there is no way that candle would effect your film. Your eyes have lenses to focus the light from the candle onto a spot on your retina, and maybe if you had the film in a camera with a lens to focus the candle's light into a spot on the film in would register. But with the film out in the breeze that candle is so far away as to be irrelevant, even though you can easily see it. A similar situation exist in darkrooms with minor leaks, glow-in-the-dark timer dials, etc which might be easily visible to your eyes but completely irrelevant to your film. On the flip side, even if you can't see any light at all, I guarantee you there is some in there floating around. Most BW films are UV sensitive, and if you are using IR film it could be completely dark in there and you could still have fogged film. So the eye=film criteria fails on both ends....it could appear completely black to you, and yet still be unsafe for your film. And YOU could be able to see light sources that are completely harmless to your film. I can tell you that a few minor light leaks around your door or a boldly glowing GraLab timer dial a few feet away may very well be completely safe. One day I had been bulk-loading film in the dark for hours and eventually my eyes adjusted to where I could see my feet because of light leaking in the bottom of my door. So here I am standing, loading film in canisters, and I can look down and see the pattern on my socks, which would have been completely black a half hour ago before my eyes got REALLY adjusted. I had been loading film like that for a long time. I didn't fix the leak. I still load film in there.
All that matters is that it is dark enough to not effect the film significantly during the amount of exposure the film is likely to have to the room. That's what matters. Not whether or not you can see it. If being able to see or not was relevant, you might as well just close your eyes all the time.
They eye test is invalid. The way to be really sure is to test...and do a proper test with pre-and-post flashing. I have adjustable safelights that I turn up until they fail the test, and they ALWAYS fail a proper pre/postflash test much much sooner than they will fail a naive "coin" test. What this means is that your print highlights and contrast might be being effected by your safelight even if you can leave the paper out for 10 minutes and still develop it to white.