Yes, rather than "some", I would say that the first dose provides the majority of protection, and the second is a booster, upping the effectiveness from the 70s to the 90s. If you are short vaccine, it makes a lot of sense to give out only a single dose to more people than both doses to a smaller group of people and then circle back when more is produced. The only question is whether it makes sense to circle back if the time elapsed is long, and this study is evidence that it does.