That was my first thought too, but I do wonder about one aspect here. Doesn't Windows' relatively slow file i/o result largely from the architecture of the kern

That was my first thought too, but I do wonder about one aspect here. Doesn't Windows' relatively slow file i/o result largely from the architecture of the kernel-mode I/O subsystem? That's the impression I got from reading up on the issues Microsoft was having trying to speed up WSL (and hence, in part, the move to WSL2). Having said that, slow file i/o probably wouldn't rank that high in the average user's list of Windows issues.