That's a bit of an exaggeration. A lot of guilds can barely fill their raid roster. They manage by strongly pressuring all raiders to show up every day on time, and to give advance notice if they need to be out.

Speaking personally, until very recently my regular raiding guild only had about 26 or so raiders who could show up every night (and another 3 or 4 who could show up for 1 or 2 of the nights). And yet we still managed to clear 8/8H.

Those of us that got heavily into EverQuest "back in the day" recall raids that involved these kinds of numbers (50+) and took place over 8-10 hour periods. It was possible to achieve with sufficient planning, a dedicated guild, and a compulsion overwhelmed the need to sleep, eat, or view the sun.

I'm not proud of those days, but it did help me realize the key to managing any large group of people: make it feel like work, make everyone believe that it is a job and not a leisure activity so that you feel obligated to stay despite a complete lack of anything resembling fun.

So, yeah, I can imagine this actually happening. If you could do it with EverQuest, you can probably manage to achieve it with Minecraft.