I'm not sure what Breezy is seeing, because I'm seeing a horse with a woefully inadequate hip, although at this stage of his development that may improve.
His neck does tie in oddly, and those front pasterns are a bit scary. He is downhill at this point in time [may grow out of it] and has a very upright shoulder that has a very closed angle. Based on his shoulder angle he might be a choppy ride though the long and over-sloped pasterns may smooth that out a little [yes the pasterns ARE a fault because they will be weaker than a more ideal leg, but he will be a little more comfortable to ride].
He is less mature than my mother's coming 2yo [23 months] and less mature even than Satin was at 20 months on the dot, so I wouldn't call him super-mature for a coming 2yo [though Satin is quite a "mature" coming 2yo]. He's about average to me, maybe even a little immature. My 2yo rather immature TB was around that mature physically when she was his age.
However, that doesn't mean to say you can't start him when you want to... as long as you keep the work load light. I know someone who will ride a 2yo 2x/week very lightly at walk/trot for 5-10 minutes at a time, and by the time they turn 3 that time frame goes up to 20-30 minutes and another ridden session is added to the week. Then when they turn 4 they get ridden 4x/week, and when they turn 5 they come into full work [6 days a week for an hour a day with one jumping session every week].
I think your little guy will make a lovely pleasure/trail horse and maybe a low-level allrounder. If his pasterns were better he could hold up to quite a heavy workload but I don't think he's for high-impact sports like jumping, barrels/gaming, cutting, reining etc.