I don't know if I class as a serious programmer, but I sort of learned from the middle out... although I started on a ZX81, and then an Acorn Electron, I only ever poked around with BASIC on both of those. I didn't start learning about the underlying concepts until after I'd started learning higher-level languages, and the reason I learned about the OS-level stuff wasn't because I absolutely needed to at that time (although in retrospect it was helpful), but because I was interested.

I think people will learn just fine wherever they start, as long as they're interested. Their interest will take them up or down the stack as far as they need to go.