Stronger riders spinning faster while drafting less fit riders is a proven technique for equalizing fitness while allowing the stronger riders to work on an aspect of their cycling.
Climbing is another area where different fitness levels are a problem. Many think that a stronger rider should lead and the weaker rider will get a benefit of a draft. That may work in some cases but a better way is for the stronger rider to ride along side the weaker rider (assuming road conditions allow). This creates team work and the stronger rider rides at the other rider's pace and can offer encouragement, if required. The slower rider does not feel the pressure of having a stronger rider behind with the concern of the speed being high enough.