How *slow* can you go on the M365 scooter?

My dad is getting older, but he's fine except for his knees. He can walk, but after walking longer than 10 mins or so he will get knee pain. Just standing is fine. He would be way to proud to use a wheelchair or "mobility scooter" (and it would be very inconvenient), so we thought about getting an M365 (or similar).

The question is, is it possible to ride at walking speed, so he can ride next to my mom while she walks? Or will the motor cut out, or is it just too wobbly at slow speeds? We don't have rental scooters here yet, so I can't try one...