As an owner who jogged about 300 mostly bombproof horses to a jog cart, there was no issue if the horse took a bit of a hold- actually comfortable and relaxing, esp if they trotted.
BUT, having never sat behind a puller or a runaway, much less follow at race speed directly behind another horse, I am sure it takes its toll, esp if it is a continuous struggle with a horse that won’t relax.
If you ever have the opportunity, try it with a horse the trainer knows is reliably calm.