Ever since Toyota Camry's got the reputation of being low cost maintenance and lasting forever. If your engines won't last well past warranty then your reputation as a company goes down hill.
Again, if they don't break the engine in themselves, they're then relying on the consumer to do it properly. You never trust that a consumer will "follow every instruction to the letter". You can't even gurantee your sales men will follow the instructions as evident by the "take it to redline" sales men mentioned already. Your opening yourself to lots of money spent on potential engine failure claims in doing that.
All the backyard myths about engine break in's are just superstition based on kernels of truth. Engineers have figured out the science behind it along time ago. The machining and precision process has caught up to the point now an engine can be broken in and ready to go after one heat cycle under a stress test procedure (as seen in the video).
And to your other points, I changed my oil at 5500 miles for the first change. No issues with an Oil Analysis test. I must of just got lucky though you know?
Not many cars come from the factory with a magnetic drain plug also. Including hypercars, supercars, sports cars, corvettes, camaro's, mustangs, and what not. Never been a chronic issue. Matt Farrah's Million mile lexus didn't leave the factory with a mag plug either.
You can hold tight to your superstition and feel good and justified if your engine lasts and thats fine. Your "Break" in doesn't have any negative impact on the engine. So you can believe you've done your self well. Engineers will just get to have a small chuckle at the people who continue to do "break" in on new cars. Driving around varying speed and rpm and every other notion under the sun the first 100, 200, 500, or 1,000 miles or whatever specific measurement your particular break in belief is. Instead of just driving the vehicle the way its meant to be off the show room floor.