What if my child explains it back completely wrong?

A confidently incorrect explanation from a five-year-old is thinking happening out loud, which is the thing you actually wanted.

Ask what makes them say that. You will usually find the reasoning is sound and one input was wrong, which is a much easier fix than it looked and one they can often make themselves.

Correcting immediately ends the conversation and teaches them that saying things out loud is risky. That trade is almost never worth the accuracy you gain.