This is far from a completely new finding. But this study has an excellent overview of how communist Cuba's supposed achievements in infant mortality and longevity are in reality the product of a combination of data manipulation and repression. By "repression," the authors mean things like forced abortions of at-risk fetuses, so that these babies would not show up in infant mortality stats.
Communist regimes have a long history of falsifying all sorts of statistics, and a totalitarian state makes it difficult to independently verify them. The Soviet Union, China, North Korea, and others engaged in comparable or worse data manipulation. The USSR also touted supposed massive improvements in health care, and claimed it had surpassed the West in that respect. Western leftists no longer cite bogus Soviet health care stats. The Cuban ones should be treated with similar suspicion. Indeed, Cuban health care (like much of their economic and political system) was actually organized in imitation of the Soviet model.
As a child I spent a good deal of time in third world hospitals myself, and remember enough to recall the contrast between the reality and the propaganda. Actual dialogue between my mother and a nurse when I was an infant (as recounted by my mother):
Nurse: Is this your only child?
My mother: Yes
Nurse: That's unfortunate, because this one probably isn't going to live.