Is it possible it's the way you're doing it & the skill & understanding you bring, rather than it being all credit to the round pen & 'join up'? I'm just saying it's not a magic bullet and it does not work *in/for the manner many believe*.
It would be interesting to know, of the total time spent handling the horses, what time in minutes and as a percentage was the join-up, compared to the time spent installing the leading respones, teaching the horse to stand still, habituating the horse to its body being touched etc etc.
To date, (to my knowledge), no one has systematically compared differences between training outcomes where the only thing that changes is the join-up component. All the research so far has compared the whole system with some other system, making it almost impossible to determine if its the chasing/not chasing bit that's critical, or all the other careful, considerate handling of the horse that comes after it.
My own training approach doesn't include the chasing bit, but does use the careful/considerate bits and I get results I feel are analgous to what I see in join-up trained horses. However this isn't scientific! All I can claim is that my horses can be kindly and sympathetically trained without using chasing.