The Moderns are also very likely gingered, and ginger can cause some ponies to get light behind or even kick. And yes--the tailer has nothing at all to do with a lack of training, confidence or "chasing". A good tailer does not chase! Not just anyone can tail--grabbing a friend to help out can be a bit of a disaster if they don't know what they are doing. The Moderns are shown in bits, and you want them pushed up into the bridle so they are set up just so and showing their best movement. My Classics always show with just me, and they know to trot out freely--but if I were to do one up and show it Modern Pleasure (and some of mine would do Modern Pleasure very well if I presented them that way--not all Classics can do Modern Pleasure) I would most definitely want a good tailer.
When I used to show multiple ponies in the various classes, I'd often have a catch handler who couldn't run--so she would present one pony in the line up, then when she needed to work the rail we would trade and I would trot the pony down and back--then trade back so I could run with my own entry. There is no rule against switching handlers in the ASPC division, and a good thing. It is much easier to get a catch handler if you can promise them they won't have to run!!