I said that I learned encounter balance from the 3E DMG about 20 years ago, and have been using the ~80% guideline is the proper balance point ever since. I did not say that I do it every single day, and I was not using the DMG to "justify my actions", merely that it was where I got the idea of the 80% balance point from.
Using consumables shouldn't be ideal. But sometimes it is necessary evil, and as I said my players were still above WBL for the entire campaign and always took more wealth out of the dungeon than they spent on consumables completing it.
Also, putting "progress" in quotes like that says a lot more about you than me or my players.
I suspect the latter is correct, which is one of the three ideas I had in my OP about why my group feels harder than usual to my players despite sticking to what I feel are the normal CR guidelines.