It isn’t a chicken that’s about to go bad, chickens that are for the rotisserie are smaller than the whole chickens that they sell raw. You pay less because it is a smaller chicken that has been cooked. The raw whole chicken is usually a higher weight than the rotisserie was before it was cooked.

The smaller chicken is chosen to be cooked because people wouldn’t buy those smaller chickens raw since the are so small so they are a loss leader to get you in the store.