And in recent times they also use good old soap and water. Especially when cleaning is a prescribed step in the manufacturing / fabrication process. Tests show it works just as well, doesn't need expensive waste disposal, and it makes the greenies happier.
I wasn't indicating that there aren't instances where water was used, but in this specific case, you want the rapid evaporation (no water in the connector contacts).
And as per water itself, it needs to be deionized water (usually obtained by distillation), not tap water. The reason is so no minerals, aka ions, can be left behind which cause problems.
Where it's used primarily, along with a saponifier (soap), is for cleaning water soluble flux off of rapid soldered boards (reflow oven or wave process). WS flux is nasty stuff (highly corrosive), so it must be cleaned off, and quickly once the soldering process is completed.
Water can dissolve or remove some debris which highly concentrated alcohol alone can not.
By mixing the two you're creating a super cleaner of sorts.
Water is a good solvent, but not in this case, and it's not the most commonly used in electronics. IPA and other alcohols are more prevalent in electronics manufacture however, due to the chemistry being removed (non water soluble oils and greases, oxidation prevention, or as a thinner in non water soluble chemicals, such as rosin based flux).
Mixing alcohol with xylene makes a super cleaner (80/20% split respectively).
Give it a try if you don't believe me (better than straight IPA, but not as aggressive as acetone, so safer for plastics).
Additionally unless you're using a pressure spray technique alone (like they do in the manufacturing line) 99% alcohol may actually be a bad thing. High concentrations of alcohol rapidly removes moisture which in turn will rapidly break down the microstructure of many materials (cloth, tish, plastics, some anodizations, etc.) which end up as debris on the very parts you're attempting to clean. You can sometimes ever see the affects of this on hard materials such as aluminum, some paints, and many kinds of plastics - where the hard material turns white. What's happening is that the microstructure of the material came apart and created a film of broken microstructures across the surface. By adding 30% to 40% water this process is counteracted.
For the last couple of years I've been cleaning and refurbishing antique and legacy camera lenses for a living. These little facts become very apparent when working with clear glass under high magnifications - as I do.
There shouldn't be any moisture in the PCB or contacts at all to cause this problem.
I use IPA all of the time, and though I'm aware of what you speak of, it's not that common a problem for electronics if the exposure time is limited to a short duration (rapid evaporation; do not let it soak). Heavier deposits have to be run multiple times, assisted with mechanical abrasion (ESD plastic brush for example), until it's removed rather than soaking in IPA. It's also a good idea to perform a test run to be sure the component packages (plastic usually), can handle the processes and specific chemistries being used.
All of this is rather overkill for what the OP needs though.
This is a different thing than the pink eraser tho. Pink erasers have a very fine grit which serves to remove micro-scratches in the gold pads as well as baked on hardened greases and oils that may be present. White erasers will only remove (and smudge) softer oils and greases.
On heavier oxidation, such as if the contacts were exposed copper, this is what I'd have recommended. But those contacts should be gold plated. Combine the fact that gold is soft, and the plating is probably on the thinner side, an abrasive isn't the first thing I'd go for in order to keep it from being scratched off.
