Not true.  I've worked on electronics since 1966 and I have used contact 
cleaner often.  I have found on relays it is more of a temp fix, but have 
never experienced harming pots.  Cleaners aren't as good as they use to 
be, but there are two kinds, one that just clean and others that have a 
lubricant of some kind.  I tend to just use the cleaner.  When tv tuners 
were mechanical things, we used stuff called tunawash and it worked on 
pots as well.  I've heard of people using wd 40, but I'd never use that on 
a pot as it leaves a film that can collect dust.
73
Butch
WA0VJR