Is 6 hours that short? Breakfast at 8am and lunch at 1pm is not that unusual and while for some that might be modest for others it could mean a more substantial meal.

Personally I struggle to sleep sitting up/on my back and don't fly cw unless I get an upgrade so a flight arriving early morning, I'll usually pick at something when I get on the plane but go for the full breakfast. I tend to hit the ground running at the other end with a full day planned so prefer to eat when I've still got a chance to sit down.