I have never heard of it described in that way -
Moreso, the creditor(s) of the unused credit cards will reduce your credit line OR cancel the card altogether for non-use sometimes with warning, sometimes without. Each of these things will affect your credit score for a period of time but if everything else is ok, it should rebound shortly.
How much a reduction in credit score will be based on how much available credit line they remove or how much credit line did you lose if they cancel the card and the ratio of used credit that you now have because part of your score is how much credit you have in play compared to the total amount of credit you have to use.
If this happens to be a very old credit line - that may count a bit more against you too.
Revolving credit like a credit card needs to be used from time to time, even if you just charge a little bit and then pay it off at the end of the billing cycle. That just keeps it in play. Revolving Credit Companies have a lot of exposure with cards that don't get used, they also get concerned if they haven't heard from you in awhile and they also get a little shacky when the economy is a concerned and interest rates are rising.
If that is all that it is - it should rebound within a few months especially if you are paying down your current debt load so that the ratio between used credit to available credit is getting better.
It's Always Something . . . . Roseanna Roseannadanna