Very simply the tanks look amazing with all those fish right form the start. I wish I could keep that many fish that quickly in my tank. Realistically they will have major filtration, ammonia, and death issues putting that many fish in those size tanks that quickly. Unfortunately, it is very simply they want the wow value of that first reveal, that makes the buyer think they got their money worth. For them it is cheeper (and likely better for business) to collect the paycheck, and correct the problems later. Thus it seems like they have good customer service. So sorry that fish died, we will replace it at no cost, sounds good to the buyer. What they fail to see is the loses were already paid for in the purchase price and/or service charges.
I think what we see on the surface looks bad. They are clearly ignoring stocking amounts, reccomended tank sizes, QT, and proper cycling practices. Now there are ways to "quick" cycle a tank, like using very well cured pre established live rock, and well aged water. This way them establishing a tank is more akin to moving or upgrading a tank, and we know that can be done quickly. If they had a 400g tank with a hidden sump with 400 lbs of established live rock, and brought a tanker truck of establish salt water. You could get a tank up very quickly, especially a FOWLR. Unfortunately, none of that can be seen on the show, and the filtreation systems seen looke more like a skimmer, UV, and cheical filtration system, not a sump system.