Yeah, that is pretty much right. 8 hours a day of running into the same thing over and over. Imagine playing your favorite game, but only level 2, for 8 hours a day, 5 days a week, for a month.
I will say, I would have killed to be testing this title. Not because I want to play it before anyone else, but because there is SO MUCH CONTENT that some really weird things can happen that will never happen in the real world, either because of what is in the game, or because of what the testers have to do to break it. It's like a totally different game than the one you buy, because the goal is totally different. Synths and mutants and raiders are obstacles to overcome to get to that valley where, for some reason, grenades bounce like a pinball and cause the audio to go crazy. Why? Because this one rock has the wrong hit detection.
Most likely, many Fallout 4 testers were assigned an area of play, and were responsible for doing everything possible, regardless of if any player would ever do it, in that area. Some testers could get assigned to check out all the Vault-Tec vaults in the game, others would be focusing on settlement building, more on finding every nook and cranny and NPC in Boston proper that could cause problems, and some would be given the 100% completion task, which can be loads of fun and a nightmare all in it's own.
There would also be times where their leads would go "Ok, everyone. test what you want these next few weeks. We think it is pretty stable and want to see how long-term progression works, so don't use any debug commands, hacks or cheats. See what ways there are to get to *Quest mark X* that we might not have covered."