No its not accurate. Factors of it include the density, moisture, how trimmed it is, how much you are compacting it.. When you finish a run you will find containers generally balance out in weight. But the weight will change from one grow+strain to the next. So the law of averages will apply to the run. But not universally from one run to the next. If you replicate your grow enough times you will know your averages lets say +/-20% but your basing it off visual cues you gain over time knowing the data of multiple runs. when you have done 5 runs of the same strain back, to back, to back. Its a little easier to say "i know when this grow finishes i will get about 1lb per gallon jug". if that were the case. or whatever your weight will be per container. But until then is no real rule of thumb for anyone.
Even then flush, no flush, nute burn, nodes. all factors that will make you think its as good as last time and will be worse or even better. Only thing any of us can do til its on the scale is 'Guesstimate'.