The article has some examples of breakage, and these are mostly using an allocator other than the system allocator which hard codes a 4k page size (Go, Chrome, jemalloc) at least for x86 and arm.
Why did they assume that? 4k pages are a feature of the memory management unit of the cpu. Optional support for large pages came to x86 with pentium in the mid-1990’s. Presumably all x86 cpus out there today have large page support, but the assumption of the 4k default is deeply ingrained.