I think having one team that works on all the mainline games contributes to BGS games being what they are. I imagine it contributes to cohesion and knowledge transfer among the devs between games, which helps maintain consistency in output over time. In an age of AAA teams churning through devs with burnout and crunch, it seems like BGS keeps a team together that has multiple years of experience collaborating, and that's a good thing.

Re: the teaser... imo, in the context of the time, people were going to believe TES had been entirely abandoned if they didn't release that teaser. Since BGS had alternated TES and Fallout to that point, there was the expectation that TES 6 would be the next game after Fallout 4; but instead, in 2018, they announced, "Fallout 76 is next and Starfield after that, and we haven't forgotten TES, it's just 3rd in line." If they'd only announced FO 76 and Starfield, TES fans would have blown up about the franchise being dead.