That is not necessary and actually can negatively affect pilot's performance in the event of a quick launch and flight.
I am NOT saying your friend lied. But back during the Cold War, I pulled Victor Alert duty at RAF Upper Heyford (F-111E) and I know there are several degrees of 'alert'.
The F-111 is a two-man crew and at the lowest level of alert, pilots must be in flight suits at all time and cannot be more than 30 minutes travel time from the VA area. It mean they can go shopping, to the gym, or if a pilot live on base, he can even go home for some booty, but if the horn sounds, all VA crews have to be on their jets in 30 min or less and g-suit up.
A higher degree of alert mean the crew must be in the vicinity of the VA shelter that contains their jet. Basically, it mean they can fly in 15 min or less. They can even be outside the shelter without their g-suits, but they must be present in the area.
The highest degree of alert mean the crew is suited up, in their jets, and with engines running. All VA crews just waiting for the squawk to taxi and launch. By this time, INS-es are fully warmed and target cartridges fully initialized. If the launch squawk come, pilots and WSOs must authenticate the launch code and voice acknowledge before they can taxi. We have gone to that level before. Today, we can admit such times did happened, but back then, it was punishable under the UCMJ to reveal when we ever had that level of alert.
Sitting in the cramped cockpit for long just waiting is physically and mentally bad for the pilot. Inactivity pools the blood in the body's lower region and can affect thinking. In the early days of the Cold War, we actually did have pilots in the cockpits of B-52s, refuel tankers, and AWACs, but we found out there were no benefits of any kind to it. There is a lot of medical literature about this.