I started practicing free-mounting while I could still only ride less than 100 feet. My recollection is that learning to free-mount was harder than learning to ride. I’m not sure where you read that it’s easier to learn to ride before attempting to free-mount. The two skills (mounting and riding), from my perspective as a beginner, seemed to be very different. Whenever I attempt to learn a new mount, I don’t feel that my general improvement in riding helps me learn the new mount much faster. However, the time I practiced mounting improved my general riding, because the technique used on mounts translated into other techniques: still-stands, idling, one-footed, etc.
Here’s my number-one reason why you need to start practicing free-mounting right now: It gives you a lot of practice dis-mounting. If you only assisted-mount, you will have less practice dismounting, and you may dismount more often when your legs are burning out at the end of your run, which makes things even more awkward.
If some other rider can explain the logic behind learning to ride well before practicing self mounts, please explain. That logic doesn’t jive with my own experience unicycling.