We should all be familiar with high enough light levels being used to completely prevent mobs from spawning in a location, but I am curious if it's a myth that there's any difference in the odds of mobs spawning when there's low enough light to allow spawns as opposed to no light whatsoever.
Let's say, for example, you have a single room, completely closed off from the outside, suspended in an otherwise void world. The walls and ceiling of this room are made of solid stone, but the floor is made entirely of glowstone. A default skeleton spawner block is floating 12 blocks above the floor with its spawn area fully inside the room. You can imagine that since the light is so far down from the spawner that skeletons should still be able to spawn anywhere in the spawn area (since spawner block rules allow things to spawn in midair) but would the spawn rates be better if the floor did not emit light at all?
I have researched this on the Minecraft wiki and found that there is only mention of what prevents the mob spawn, and nothing in the chain of conditions about reducing the mob spawn's odds of success when light exists in low levels. You can find all sorts of mob grinder build videos where the operators run on the assumption that the room ought to be pitch black for best spawn rates, claiming that you should allow no light from your collection room or your redstone wiring to filter into the spawning area. Could this assumption actually be just a myth we need to validate/bust?
Please substantiate your response. Personal experience and hearsay are okay, but good sources/statistics earn best answer.