Absolutely not accurate at all over the years I have had animals that were 18 months and anywhere between 1300 to 1800 grams.
I have had a few animals also that were 3 to 4 years old that were barely breaking the 800 grams mark.
So what makes the difference and why well cared for animals raised from hatchling can show such a descrepency making any chart completely inacurate?
Well there are a lot of things going into the size that an animal is or will be: size out of the egg while most average 45 to 65 grams some will hatch at 30 grams some will at 90+ grams. (That means they will not eat the same prey size from the start), the there is how fast an animal get started, some will take their first meal a day after their first shed, some will take it 8 weeks after their first shed
After that there is feeding frequency, prey size, skipped meals, fast etc.
And at last there are genetics some animals will remain under a certain weight for most of their life if not all and some will reach much larger sizes.
Bottom line it's not about weight, charts, comparing your animal to someone else, it's about the animal being healthy, fed right (neither overfed or underfed) and the animals having good body proportion.
Weight is a number and that's all there is to it really.