Well, maybe he really liked to swim.
Ranger School like to killed me at 23 and I could run all day and do sit-ups all night back then. In fact, one morning one of the Cadre stopped me and asked me how old I was... I told him “23”... He said “You look 63”.
I’d have never made it through hell week at BUDs either before or after (recovering from) Ranger School though.
Q course was pretty easy physically, and I found it mentally easier too... Because I wasn’t as exhausted and stressed as in Ranger School. You have to be more competent at a wider variety of tasks, but at least you get more sleep, can catch your breath occasionally and stop to think.
IIRC, Former SMA Glen E. Morrell was in his late 30s or early 40s when he got tabbed.