(Author here:) I strongly agree! It should not require an understanding of the kernel's execution logic to be able to understand the limitations of shebangs. I think this is stupid design and I perhaps should've highlighted it even more as such.
A couple years ago someone attempted a patch to the kernel that would at least fail loudly in the case of oversized shebangs. This ended up causing problems for NixOS which, being Nix, already was using oversized shebangs with lots of long nix-store paths. They were previously being silently truncated but still working, and suddenly all those scripts failing caused a lapse in backwards compatibility! So the patch had to be undone and we haven't gotten anything similar since.
A couple years ago someone attempted a patch to the kernel that would at least fail loudly in the case of oversized shebangs. This ended up causing problems for NixOS which, being Nix, already was using oversized shebangs with lots of long nix-store paths. They were previously being silently truncated but still working, and suddenly all those scripts failing caused a lapse in backwards compatibility! So the patch had to be undone and we haven't gotten anything similar since.
See https://lwn.net/Articles/779997/ for more info.