Without being critical of the crew in any way, whom I think did a great job of getting the thing down in one piece. One has to ask this question?
If the lap strap was loose enough to allow the extraction of the Captain from his seat during decompression, It would have been loose enough not to restrain him in cruise, during e.g., turbulence, which in my opinion is one of the main considerations for being strapped in at all times while in the seat. IMHO the lap strap can be secure yet comfortable, to provide adequate protection.