Non sense. Linux makes many details about computers much more explicit than Windows does. Even installing Ubuntu teaches you something about how computers boot, what partitions are and file systems do. Linux also makes it easy to get started in programming on the OS level -- thanks to the Internet it is way easier to find information about how everything works.

So from a learning experience perspective, a kid tinkering with Linux might gain more insight into how computers work and than, say, on Windows or Mac.

That's today, but it wasn't so initially. You'd learn about your monitor's scan modes, how the disk is structured, dumping bytes between devices, optimizing for load by placing bytes on the outer sectors of floppy disks, using RAM as a disk to speed things up, and whole lot of "useless" things that build machine sympathy.