Really? Above 10.5K? Where and when? I've never seen (or heard of) bears or signs of them at that altitude or higher in the Eastern Sierra....
Bears are crafty, but they cannot defy the laws of physics. If a bear got his food it was not
They can climb trees, and YES it was hung very properly. Bears in Yosemite have been getting properly hung food for years. That's why canister rules are so strict there. They climb up above, jump from higher in the tree, grab the bags on the way down. It's been observed by more than one person....
Poop appears above 10k in Sequoia and Kings, so far, in my personal experience. Tablelands - we visit each year. Up on the passes - they do share our trails.
There's a bear in Paradise Valley (Kings) that can get a lid off a Bear Vault by a different method than Yellow Yellow back east - he tips it over and does CPR on the can. So put your Bear Vault in a locker there... For a while, there were signs (this was a long time ago) instructing you not to run away from a bluff-charging bear in SEKI who learned that people drop their packs if he intimidated them. He wouldn't hurt you, but he'd huff and run at you.
Bears can get into third story cabin windows.
I don't think you talk to very many people out there... I hear all kinds of things and see all kinds of pictures of evidence that bears are smarter than they appear most of the time. There's a video in existence that documents a bear hunt where, after being shot, the bear pauses to scoop mud into the wound before taking off into the trees.
So yes, I KNOW that bears can get a properly hung bear bag. They don't do it consistently enough that people will believe it - there are those, like you, who swear they've never had a problem. But experienced backpackers are not exempt and the bears get their properly hung food just as they do the food people try to sleep with, or put under a pile of rocks, or leave in the side pocket of the pack. That's part of the problem. The non believers will continue until they have a bad experience themselves, resulting in another bear taking one more step toward being a nuisance bear - which eventually get killed. Yep, I KNOW that happens too, rangers shoot them and they become part of the ongoing study of habituated bears.
They have also breached the bear canisters, including the models I have and use - but so far, this has not been a replicated behavior that's turned into something all the bears are doing. Crossing my fingers that people won't just let the bears play with the canisters all night long - drive them away ... don't give them time to figure out dropping it on granite works. I look for tree wells to place a canister in, or bury it under heavy granite flake as an early warning system so I can get up and pitch rocks.
The most frequent incidents are where the people flock - Yosemite, and the problem is growing in SEKI, as rangers have been talking about canister mandates becoming more widespread there. As people research online and start to explore more of the Sierra there'll probably be more than occasional incidents elsewhere. The only cure is prevention, IMO, which is why I finally dropped the dime on a Bearikade.