See, this I don't get. I really don't.
In what way is 5e like AD&D? The classes aren't even remotely close. What we call a fighter in 5e would be completely unrecognizable on a table playing AD&D. He still uses a sword? Maybe? Virtually none of the mechanics of AD&D exist in any shape or form in 5e. Right from the stat bonuses all the way through, nothing of AD&D, other than maybe proper nouns, exists in 5e.
Bounded accuracy is identical to how 4e's escalating numbers worked. All bounded accuracy is, is 4e math without the level bonuses. And, in AD&D, that never happened. In AD&D, you went from very low chances of success to virtually guaranteed success as you advanced levels. Since AC was (more or less) static, and your THAC0 increased by level, your characters were going to hit more and more often as they gained levels. In 5e, because of bounded accuracy, your chances of success remain largely static at any level.
Heck, look at how thief skills worked. At 1st level, you were going to fail far more often than you succeeded. By high levels, the reverse was true. The task never actually mattered. You opened a lock, full stop. The idea that one lock would be a different difficulty than another didn't exist in AD&D. You opened a lock X% of the time, dependent on your character's level.
It absolutely baffles me when people try to link 5e to AD&D. There's just virtually no commonality.