That was certainly my experience. When I was younger I we decided to get into 4-H and we started small - with a pony. He was awfully cute but very cranky. He'd nip with regularity and he'd let you ride for awhile, then do a quick little hop-shuffle and put the rider on their butt on the ground. We quickly moved out of cranky ponies and found a large Morgan/quarter horse - huge but gentle.
The trouble with ponies is often that they are too little for an adult rider to ride and train them, and so all their training has been done by little kids who yank them around. If they are a little rank it is because no one puts the time into training them that they would a full sized horse, they think they're more harmless because they're small.
I got a beautiful black shetland mare for my 5 year old son.Her tail dragged the ground. Did not bite either. She was broke to the cart. Problem I did not have a cart. So we used her on a long rein. Turned out she had a turn for speed when in the ring and bucked quite hard. My son flew off many times. He finally got good at staying on the bucking. However I could not ride and train her due to her size, just too small. Then I snapped my achilles and was on crutches for 5 months. Could not lead the pony. So we let her off. But that year we did not have a drought and the grass was good. So you guessed it , she foundered. By the time I was on my feet, she could not be ridden. I gave her away and lost the purchased price.
This was a pony about 7 years old.
So my lesson for small ponies is that cute but not worth it. Can only used them for a couple of years and kids out grow them fast. Then just a waste. Ponies go through so many owners that they do develope a lot of bad habits. I have known Shetlands go through the barn doors with a rider and just duck under the rope to keep loose horses from runnng free. Of course the rope sweeps the rider off. Ponies open stall doors and get into grain bins.
They are smart.