We're different than most in that we like to arrive a little later. That way we almost always encounter no lines, no waiting, and our cabin is usually ready for us as soon as we get onboard. So we are able to casually board the ship, drop off our carry-on luggage in our cabin so we don't have to lug it around, and then go up to a less-crowded meal.
If you get there early, there's almost always long lines (we hate standing in those lines) and it's chaos trying to process everyone so they can get onboard. Then, since most of the time the cabins are not ready for occupancy until about 1:30, everyone takes their carry-on luggage and heads to the buffet area on the Lido Deck. So it's very noisy and becomes very crowded with people pushing and shoving to get as much food as they can as quickly as possible. Sorry, but to us that's just not a fun way to start a nice cruise and much rather spend 2 hours less time on the ship to avoid all the hassles. But to each their own; everybody is different on what they like to do.
Don't pay alot of attention to those assigned or suggested boarding times as they're not going to say you have to wait until your time is called. It's just their way of trying to stagger arriving times in an attempt to make it less crowded since most people want to get there and on the ship as early as possible.