Fortunately it is premature (spoiler)

Trying to understand this statement since hearing the first time hearing it seemed to be a contradiction. For example, it was premature for Weyland to meet the engineer, but why fortunately? David says this to a sleeping Weyland. He thereafter get confronted by Vickers. he says Wayland told him to Try Harder. He then goes for the ampules. shaw says what killed the Engineers, and the scene changes to David breaking the top of the green glass phallic goo container. I am thinking it is in reference to a life form in the ampules. Someone else posted this theory about the four tubes being life forms and it all seemed to connect for me. Still, it would require knowledge of what was in the ampule. David could have gotten this information from a scan or reading the hyrogliphics. We also have to assume Weyland was directing David with no consideration of the consequence or who was hurt. That last assumption is pretty easy.