Well, it’s all shades of gray, right?
Some factors i would throw into the mix:
People who’ve lost their fitness, and are trying to get it back, are usually categorized as hobby joggers in my mind. Even when someone has competed at a high level before, or has a ton of genetic talent, i think that being 30 pounds on the heavy side or huffing and puffing to string two miles together, would safely qualify someone has (at best) a hobbyjogger.
Also, A lot of stopping and starting is very much the way of the hobbyjogger. (I know this one from personal experience!) If you can’t seem to string together more than three or four months of consistent training, you are not in the same league as people who have years of lung development and legit miles on the odometer.
A third factor might be, a Once N Done mentality, seems very hobbyjogger to me. If the fun wears off after completing your first Whatever-K Roadrace, and you don’t wanna train beyond that, you’re probably not really a runner in your heart.
Those are my thoughts! I could go on, but won’t add more right now.