As I’ve said in previous posts, I’ve long suspected that the real story is that the “flat” design (first for the iPad line) is what is making these normal variances more noticeable. The last product made with a similar design was the iPhone 5/5S, which was much smaller. It had its own cosmetic issues (the easily nicked chamfered edge). My guess is that Apple might return to a more rounded design if it sees a change in sales trends or complaint activity, just as it did with the iPhone 6 to the present. But the flat design has some advantages, such as easier integration with the Pencil 2.
The point is that this is a cosmetic issue. There’s no evidence that anyone’s iPad Pro has stopped working because of the small “bending.” Of course, Apple is a company obsessed with aesthetics, so if it sees that “bending” is an issue with the current generation it will look to make improvements in future generations. But every design of every Apple product, even back in the Steve Jobs era, made trade-offs between aesthetics and functionality. Steve Jobs approved the G4 Cube that literally overheated and cracked. He also probably lost millions of sales of white iPhone 4 models trying to get the right tone of white. He wasn’t perfect.
Your theory is totally plausible.
And it is absolutely true that this is a cosmetic issue.
But for a company that's stock and trade for decades has been aesthetics, this kind of thing is especially egregious. Steve was notorious for his "we have exacting standards" and "we won't ship junk" speeches. That's part of why when these things happen, they get more press than they would coming from other companies.
But that's very, very different from what the other fellow said, which was, "all products have tolerances so this is OK." That exhibited faulty inductive reasoning—and it just didn't pass the smell test either, which is why so many people are up in arms about it.
It's also the kind of thing that really should have been noticed in prototyping and QC.