A horse can be comfortable, relaxed, enthusiastic and healthy without ever going "on the bit". "Accepting contact" can run the gamut from "seeking contact" to "submitting to contact". To work the horse correctly, IMHO, one would ride in a way that encourages the horse to WANT contact - to SEEK instead of merely SUBMIT. At the seeking stage, I would expect the horse's nose to be well in front of the vertical. It looks to me like the rider is requiring the horse to submit to a frame, not to seek contact as helpful.
The horse is not "rounding". Honestly, horses do not round up in the back. This diagram shows what they can do:
That is the outcome of this fact:
What is often called "round" is a result of the horse tucking under at the pelvis and lifting at the withers. The horse in the pictures shows no hint of either. It looks to me like the rider is wrestling with rather than properly riding the horse, requiring an artificial frame in a way likely to cause resentment instead of willing cooperation.
There is an old book called "Common Sense Horsemanship". It is focused on jumping and you might not be interested in what it says about position. However, he argues for three levels of "control". His first stage includes a lot of work on slack reins while horse and rider learn to move together without relying on reins. His second level teaches soft, sustained contact. He considered that the level most riders should use. The Advanced stage was only for experienced riders. It included how to put the horse on the bit and teach the horse and rider dressage type of movement. The book has detailed chapters on how to teach each level - and the prerequisites for each.
That seems like a reasonable progression for both horse and rider. Trying to get a horse to go "on the bit" and "round up" without first building a solid foundation at the first two levels seems counterproductive. "High School" riding should only come after success at the lower schools. Otherwise it is like dropping a pupil into high school without having them go thru elementary and Jr High first.