Of course there is a difference. MMM doesn't have to do what he's doing in order to pay for a place to live and food to eat. He doesn't have to stress out about losing his income stream. He basically has hobbies for which he gets paid.
In your retirement, you'd choose to walk and travel and read books. Those are good hobbies! What if eventually you want to get into something like woodworking (a very popular hobby)? What if - gasp - you sell some of your woodworking creations for money? Does that invalidate your retirement?
If you sell those wooodworking creations for money and you keep the money - yes, absolutely. Why don't you give those woodworking creations away for free if you don't need the money? or why don't you donate the money you earn from them to charity - if you don't do those things, you admit you need that money for something that you can't afford otherwise. In that case, why not just work a job? I mean if you love woodworking and do it for money, you just have a job that you love, which is fantastic. but it's a job.
In the woodworking example, you may only have room for so many chairs around the house. And, if you don't really need the money, you make what you want when you feel like it. That's a lot different from the typical job.
Needing money isn't binary in any case. I may or may not need more money. But maybe I'll be glad I had it some day. Of, perhaps unlike MMM, maybe I'll buy something or take a trip someplace with the extra money that I wouldn't have otherwise done.
needing money is pretty binary, in my opinion. If I can do all the things I like without working at all, then I have enough to retire. If I occasionally need more money to do some of the things I like and I need to work to get it - I don't have enough to retire.
I'd probably like to hop on a NetJets when I travel but I'm not planning to hold off on retiring until that's a reasonable option. Pretty much everything is about tradeoffs.
Of course you can do that too. Leisure is awesome. I think I'd do a lot of that myself.
I don't think I'd give up programming though. I really enjoy it. Maybe after tinkering on a bunch of my own projects that nobody ever sees, I would get bored of that (pretty sure I would anyway). I'd probably get an itch to do something that other people can use too. And then it's likely there'd be money involved.
But also, "going to 3 different part time jobs" isn't really a good way to look at it. If someone asks you "hey, do you want to help me build a deck?" , there's a world of difference between saying yes because you need the money vs. saying yes because you enjoy the work and want something to do.
I would not underestimate being in the position to walk away. Even if you never act on it, that feeling of control is worth something. (see also: "fuck you money").
to me the point of retirement is to be able to wake up at 9 and go for a walk or travel or reading a book. Not going to 3 different part time jobs.