My son was huge for his age, and very slow to train completely (although once he finally was, he was usually dry through the night, to my amazement). I would have occasionally put him in a pull-up up to about age five (he also didn't really grasp the difference between pull-ups and underwear--even after he was trained he would not have been either upset or viewed it as a license to go--possibly because we were using Goodnites due to his size and they're more like underpants anyway, even then). He is also one of those people that when he has to go, he HAS TO GO!!! So at an amusement park if I was worried about lines at four and a little bit... Possibly. Although Disney is very well supplied with bathrooms.
He pretty much never used a stroller after two though. He actually bent the frames of a couple and that was back before you could get ones for older children that looked like regular ones. He was also pretty good at keeping up with the grown-ups, if somewhat challenging to keep track of (not a runner, but a Houdini).
Every kid is different, every parent is different, but it does strike me as a very odd thing to do with an older child who isn't accident prone.
And if my son ever runs across this post, I suspect he'll have a few words for me...