More directly: He only expected his code to be used in Windows NT and made the fatal flaw of thinking that just because he slapped it together in an hour it would be easy for someone to rewrite in the next version of Windows to up the limit.

Instead the code sat untouched for decades as the limit slowly became more and more unreasonable.

IMHO the real issue is the artificial limit. Instead of straight up disallowing you from creating large filesystems, it should have had a dialog box warning about small files being inefficient but letting you make it anyway.