Do people actually bother doing this ?
I never have. But then, I have many uppers, and few lowers. It's a modular platform to me.
One lower might see 3 diff calibers are 5 diff barrel lengths in the course of a month.
I guess, if you know for sure that's the only config you're ever going to use on that lower, then it might be worth the trouble, but as you venture deeper down the AR rabbit hole you might find that just doesn't happen in practice.