I don’t think it’s all that unexpected. My unscientific feeling is this just confirms what they already know, dark matter dominates. And the outer bands only contain a small amount of the mass in a galaxy. Notice in my graphic that the measurement uses hydrogen gas for the outer bands.
I think the value of this new finding is represented by this statement:
“This is an important result because knowing where a galaxy ends means we astronomers can limit our observations and not waste time, effort, and computer processing power on studying data from beyond that point,” said Meurer.
You’re probably right about that. Whenever I read about something in science that I don’t understand (which is quite often nowadays), I expect it’ll to lead to some kind of breakthrough. It never does, lol.