I Think Stratt Was Lying
I think Stratt was trying to manipulate Grace when she said she only kept him around as the other science backup.
I think that he was Stratt's backup.
Stratt had back ups for the crews, who were essential members, so why wouldn't she have one for herself? If she died in a tragic car accident, the Hail Mary could move forward with the other department heads, but Grace was by her side with most of it so he would be the obvious replacement. DuBois and others even referred to him as the number 2 on PHM.
I think him being coma resistant was a plus for her but he was pretty involved in all parts of the project before they tested for the gene. She thought upsetting Grace would make him overcome his cowardice and join the mission, but it didn't work, that's why she was real rude with him when talking to him about going on the mission.
What do you think?