Hitches also weaken the strength of your rope. The first hitch would split load around the tree so it wouldn’t be any worse than the normal girth hitch around the tree, the second hitch is a single line hitch and the carabiner locks it into place. As long as the system is tight, I wouldn’t worry but as per usual, a fall with slack and I would worry about that hitch snapping if you were on that particular leg. Overall I do not truly have a concern though because he is using it as a redundant connection point. Also if you are worried about the carabiner being the point of failure, a steel delta link would also work there in place of the carabiner