Yes, your bosses have been too incompetent to notice. Yes, if you only put in 5 hours, you are not delivering at your full potential. You are very unlikely to be delivering "10x Developer" work. I have no idea what your company size is, but I would wager that the top developers at my workplace land 10x as much code as you (and solid, well-tested, and efficient code). Yes, you are lazy. I don't know what else to call…
It’s unfair to quantify it as amount of code, it might be excellent but longer programs and complexity isn’t always better for debugging, understanding, and maintenance even if performance is better simpler code that is lazier isn’t always worst.
But all things more-or-less equal, if one guy is landing 15 lines of code in the repo a month, and everyone else is landing hundreds a week or whatever, then that guy better be able to show that he is actually tackling really tough problems.