Guessing he's thinking about the potential for traffic getting out of and back into the airport, potential delays with the monorail if you use that, potential delays with public transit, and potential delays getting back through security.
Even with a full 5 hours, which you might not have if the first flight is delayed, that doesn't necessarily leave a ton of time at a restaurant if padding things to account for all the potential delays. All depends on where you are on the risk versus reward scale for grabbing a meal offsite.
I would probably just hang out somewhere in the airport myself. Or see if I could change the flight to leave more time between flights to relax.
This was my thought - 5 hours isn't exactly long.
Work backwards from takeoff.
Assuming 5hr between scheduled land and scheduled takeoff:
30min to get off plane and to car pick up(taxi/uber)
30min to leave airport and get to restaurant.
Assume leave restaurant 2hrs before takeoff (30min return trip, 30min through security, get to gate 1hr before takeoff)
That leaves approx 2hrs to sit and eat.
Less if 1st flight is delayed or increased traffic/security time.
(Note - We're the people who show up first at the gate so we wouldn't leave airport and risk it).