First thoughts..and then I'll read the article!
It's my experience that this is usually related to folks transporting dogs loose in the back of pick up trucks. Dogs have been known to jump or fall out and cause massive accidents in which *people* and the dogs are injured or killed. In addition, dogs in these situations are subject to heat stress and cold that falls under other animal protection laws.
I actually don't think that it should necessarily be a higher or lower fine for one of the other--just that there should certainly be penalties for children or animals.
ETA: Now to add, I do agree that they are a huge distraction when riding loose in the car, both before a crash, as a possible or probable cause, and after the crash when they either are injured or are running thru traffic and causing more issues. A loose pet in the car, climbing over the driver, getting under the brake and gas pedals, knocking the gear shift, blocking vision, is a HUGE distraction. I had numerous clients who's dogs were such a distraction in the car that they hired me for private training lessons in their home, b/c they didn't want to drive with them! I had one client miss the first class b/c her dog jumped out the half open car window on the INTERSTATE, and he nearly caused a wreck. It was such a big deal that I showed clients at the first class ways to restrain their dogs in the car and really pushed that they use something every single time. It still shocks me when I see folks driving w/the their dogs in their laps or with half their bodies out the car windows.