I think I can add a little clarification here. It’s not that progress bars are impossible to implement, it’s specifically time-based progress bars that are impossible for the simple reason that you can’t predict how long the task is going to take in the user’s computer.

That being said it’s perfectly possible to implement task-based progress bars. If you have 100 resources to load before showing the next scene, the progress bar can advance 1% for every resource. Some games do that. But what the devs in the mentioned tweets are saying is that doesn’t always “feel” good. If you have 99 small resources and 1 huge resource, to the user it’s gonna feel like it’s “stuck” after flying through the initial 99%. So what they do is voluntarily make the first 99% go slower so the last 1% feels better (and other variations around that).