This just seems tautological, good = good. The question is whether it's a good practice in general. And, the answer, which I'll stand behind, is "absolutely not."
For the most part I agree, I was noting the exceptions because they end up being relevant. Every group has its own dynamic, and what we tend to talk about here is much closer to "etiquette" because you can't really be sure of anything where people are involved.
I don't recommend
hoping for certain exceptions, I just think it's important to be prepared for the likelihood that you are unprepared. If you enter a new group with a healthy philosophy about how to handle things and a good attitude, you will likely find things work out most of the time. The problem is that "most" can be as little as 50.000001% of the time. In the presence of more than one option the "most prevalent" can be infinitely smaller, just so long as the other options are smaller than the "most prevalent" still.
So you may see it as forcing a sort of method-acting on the players, but for all you know that will not only WORK but it will work well. It's not such a horrible thing to have a bunch of level 1 characters with some overlap, because they have lots of room to grow apart. It's also not so horrible to have a group that is extremely strong in one aspect of the game while weak in another, that just means you emphasize it when you work together. Method-acting works for some actors, not for others. Roleplaying that way works for some players, not for others. You don't have any idea what kind of batch you have until you've played with them.
Do I think it's a good idea all the time? No I don't, I just don't think it's as bad an idea as people are making it out to be, if only because players and groups can be so wildly different from each other. I've played with multiple groups of all-jokers, not one of them took the game seriously or even knew how to do so. I've also played with players who took the game way too seriously. How much fun I was able to have had a lot of variables, and while I do my best to have proper etiquette, sometimes it's not necessary. Sometimes it will get you left behind because the obvious thing to do is keep your mouth shut, other times it gets you way ahead because the group wasn't going to work well until you got there with your correct way of doing things.
"MOST" of the time things may work a certain way, but anyone who plays a dice-based game should be very familiar with how much one game can be different from another. Statistically a 51% chance of success isn't much better than the 49% chance to fail, it's BETTER for sure, but not so easily controlled as we'd hope.
Even when "most" means more than 51%, or 61%, you're still talking about people who are extremely variable.