'Dwarfism' is the incorrect term to use and what you are suggesting is not the case. I would agree that the exceptionally large individuals in many populations have been culled as trophies. Where growth continues with age, such as in reptiles, all this does is to alter the age structure of the population. The average size for age remains unchanged as does the average size at which sexual maturity occurs. If you were to calculate the change in average size of a population, you would need to include every living individual and their size. When this is done, for most populations the difference would be totally insignificant. The same is true of animals that have increased growth with age for certain structures, such as tusks and antlers.
For populations such as the saltwater crocodile, where there has been intensive harvesting of all age groups over a substantial period, there will be a significant drop in average length. Once again, this is due to a change in the age structure and not the genetic makeup of the population. If there was any genetic selection going on it might be for animals that are more secretive and wary as a result of their genetic makeup. We know that crocodiles can learn behaviours and becoming wary is one of those learned behaviours. The latter will minimise any effects of the former.
Male crocodiles grow faster than female crocodiles. An average male saltie will mature at around 3.35 m and around 16 years of age. A female will mature at around 2 to 2.3 m after about 12 years. I find this more informative than the term "slow".