The learner who asks for a slower pace is still asking to participate.

A request to slow down is easy to hear as reluctance, or as a drag on the group, when it is usually the opposite. Someone who has stopped wanting to be there does not ask for anything. They go quiet and drift out. The request itself is a sign of investment, and how it is met decides whether the person stays.

When somebody asks for more time, answer without any note of cost in your voice. Repeat the part they missed rather than the whole thing, and check whether the pace is working for others as well.