But if a horse – due to size or anything else – cannot make the time at a safe pace, and cannot find time-saving routes that are perhaps not possible for a bigger horse, then the outcome needs to be accepting time faults, not traveling at a dangerous pace to keep up with bigger-strided horses.
For the pair in question, I don’t know if the pace is the rider’s decision, as a strategy to minimize time faults or otherwise, or a result of the pony being very difficult to rate.