Yes, it is weird, but it happens only in a vacuum.
I wonder if "peeling" tape in air does something like drop the frequency of the emissions by a few octaves compared to the same effect in a vacuum. I have always seen light coming from tape being peeled. It's very obvious in a darkroom setting, where I used to do quite a bit of work.
Even peeling masking tape too quickly can fog your paper.
I suspect what happens in air is that the electrons never reach high velocities as they travel over the gap due to repeated collisions with air molecules. Stimulated photon emission in this case depends on the free electrons knocking the electrons in the atoms they strike into higher energy levels, which then emit a photon when they return to a lower energy state with a wavelength proportional to the difference between the higher and lower state, so a succession of little knocks will produce a bunch of low-energy photons, if it produces any at all (energy states are quantisised, so there may be insufficient energy in a collision to cause any change in an electron's energy level), while one big collision will produce high energy photons, possibly in combination with lower energy photons, since electrons that are raised by multiple energy levels often hop back down, a level or two at a time, emitting a photon with each hop, rather than jumping straight back down to their resting energy level.
I tried peeling some tape in the dark just there, but I didn't see anything. It's not very surprising though; we don't get much static building up here, since the damp air quickly dissipates any surface charge, so there wouldn't be much of an electric field to accelerate electrons.