Theyre all different, just like us humans. Not everyone hits puberty or starts to wrinkle at the same age or weight lol.![]()
In regards to feeding him, the gram weight of the prey in reference to the gram weight of the snake is the best thing to look at until they reach about 500+ grams (in my opinion). I feed 15% of the body weight until that age, at which time I start feeding based on width of the widest part of the body. 15% of your snakes body weight (at 260 grams) would be 39 grams, average weight of a rat weanling. Some people feed 10% of the body weight and that works fine too, I just personally feel it is a bit on the smaller side for meals.
And pet shops do tend to underfeed their balls and boas in particular, because they follow the same feeding guidelines for colubrids as they do for constrictor snakes. A rat fuzzy would be perfect for a corn or king that's 260 grams but much too little for a ball python or boa of the same gram weight.