That's how I learned it. My dad got tired, let go and stopped.
I noticed it was suddenly much easier to pedal, so I turned around to see him standing 30ft behind me, then I crashed.
Getting my 5yo to accept that he can peddle and balance by himself; takes longer than the ability. He used to crash once he realized I had stopped balancing him, sometimes it would take a minute or more.
It's a lot easier if you get a balance bike first. They'll naturally try coasting because that's fun, so all they need to figure out is pedaling to move on to a real bike.
I did that with two kids, and it worked well both times.