Is it weirder, that you can pass an variable precisely into argument 4? You do need to pass information to a subprocess and there needs to be some agreement on what means what. Sure, maybe you could use names instead of fds, but that sounds needlessly complicated.

That’s like saying you could use positions to specify function argument access (as in assembly) instead of variable names. File descriptors being numbers that are likely array indexes in a file handle seems like a leaky abstraction. Having a namespace that a parent process share with its children seems like a much cleaner design.

A way to pass a defined list of handles to a subprocess (or a friendly other process) makes sense. Having that mechanism be direct inheritance of those handles with the same numbering as the source is obnoxious.