Realistically, any company investing in one of these robots is going to make sure it's right for their workflow and that they're using boxes capable of being lifted this way.
Would that happen before or after that company already sunk money on one of these robots?
Most boxes are designed to withstand inward pressures, not necessarily outward. And those specs are based on a lot more thorough of testing than "well we tried it a couple times and it didn't break, so I guess we're good"; I'd need to see one of these handling a lot of boxes without issue before I'd throw it into a warehouse.
Humans are only expected to be able to life 50lbs, you can go a little heavier, but it is no longer a weight that you can safely expect anyone to lift. You need to hire for strength to go above 50lbs. At 75lbs two humans are required to work as a team to lift for safety reasons (weight lifters can go beyond 600lbs alone, but not workers). I'm not sure where the next cutoff is, you soon need mechanical help to move anything.
Weight lifters can go beyond 50+ lbs, safely, only if the weight is basically in barbell (or dumbbell, or whatever) format. A large 100lb box isn't being lifted by any smart weightlifter alone.
The World's Strongest Man format contains a number of events that are probably a lot closer to real workplace lifting tasks than barbell events are https://en.wikipedia.org/wiki/World%27s_Strongest_Man#Compet... . Though of course those full competition weights are very much an upper bound and wouldn't be viable as everyday one-man lifts even if you hired elite strongmen to be your warehouse operatives.
OTOH 73kg (160lb) full beer kegs still get a fair bit of one-man manhandling, and to be a proper professional scaffolder you have to be able to lift a full-length scaffolding pole (just under 30kg, apparently?) from flat off the ground to straight up above your head, partly one-handed in one smooth movement, several times a day routinely.
Hopefully no one that handles beer kegs for a living is lifting full ones. They have special dollies for handling beer kegs, they even have special attachments for fork lifts for picking them up. I've never been to a brewery where anyone was picking up beer kegs by themselves.
You've also never been to a bar where the owner is too cheap to buy one of those dollies. Or rather you have, but you've just never been to the back of the bar where a porter is lifting those full gets up and down a rickety set of stairs.
as the person below commented strongmen train for the "atlas stones" event which involves lifting (arguably more difficult) spheres weighing from 50 to 339 pounds and placing them atop a shelf. there are also plenty of people that do "tire flips" (myself being one such person) where you lift and flip tires ranging from ~100lbs to >500lbs (and i'm not some kind of 99 percentile lifter).
As far as I can see, boxes are picked up from one side, or the top. Some boxes would collapse due to this uneven distribution of force - a human worker would normally pick up a box from both sides, or the bottom.