Yes, if you are high enough that the atmospheric pressure is equal to the vapor pressure of water at room temperature, it will begin to boil. I assume the pressure is low enough in orbit. The trick is that as the water evaporates, it will cool. It may even freeze depending on how much water you have. It takes a while to freeze water with a vacuum, but it can be done. As it gets cooler, it evaporates less slowly. When I’ve done this on earth, the water isn’t really even boiling unless you shake it. The difference is that on earth, the surroundings are providing a heat source.
At a point called the triple point, you can actually have water freezing and boiling at the same time: To make this happen, you need a pressure of about 0.006 atmospheres. At any pressure below that, you don’t get liquid water at all, just a direct transition from solid to gas or vice-versa.
It takes longer, but the 3% is well off the mark.
To start with, you are not cooking at 3% cooler, because freezing (the zero of the Celcius scale) is essentially an arbitrary reference point. Absolute zero would be less arbitrary, and using that, you are only <1% cooler.
But that is still wrong. Cooking, like most reactions, doesn’t respond linearly to temperature. Others will chime in, but the rule of thumb is something like twice as fast for each 10’C rise…so a 10C (“10%”) drop in temperature doubles the required cooking time.
And yet that is still not quite right, because the polymerization and oxidization of the protiens in the egg isn’t a sigle, simple reaction.