It has been a number of years since I have trained dogs for people.
From your description I would have considered the dog done and moved on. But, I'd have kept in mind that the dog didn't progress to the ideal goal of a one cast exit. It may never be an issue in the future. Or, it may need to be addressed in other ways in the future.
I think, with some dogs, staying on some drills too long is detrimental to the dogs training. And, can have impactson the dog for a long time.
I would err on the side of moving a little too quickly and go back if necessary.