> I distinctly remember him talking about how worthless having a file system is on a server, or for that matter an operating system.

If I recall correctly, his statement can be more charitably summarised as noting that many of the functions of an OS or FS are not useful in the specific use case he had, which was running a single program serving a website. He would therefore prefer to not have the additional complexity, attack surface and performance overhead. I do not think that this is very controversial? There are of course trade-offs involved, and he did mention that he was planning on running Linux as a way to get device drivers and something booting with reasonable effort, at least initially.