There were similar issues back in 2004 (when I was working in after sales service for a computer parts retailer). I would have thought that in 10 years, heatsink and motherboard manufacturers would have figured it out…
Intel specifies the same 50lbs of pressure maximum as with the previous generation. Either they should have lowered it, but didn’t test, or the heat sink manufacturers have been ignoring that limit — and didn’t test. Either way, the substrate is thinner, and the bending makes sense in that regard.