I suspect there's some truth to that. The predominantly piscivorous diet in the wild could result in faster growth rates in nature. Hobbyists who feed their dats live feeders, CDM for example, have reported surprisingly rapid growth rates even in captivity.
it costs to much to feed them on feeders hear in the UK i chould put 100 feeders in and they are gone in 20mins at the price of £50
i have one tiger that eats meal worms and his growth is much faster than the rest
i find the thin bars and silver tigers grow a bit faster than ST and NGT