right, but that's not using X *as X* or to interact *with* CLI. It's using X just as a set of terminals for CLI that's completely unaware of X.
X, the system (as I understand it), does not use CLI. It sends and receives messages of its own devising and format but doesn't expose these to the user or use the CLI or pipe system to do it (except for some command options for programs which are mostly now ignored)
Tcl/tk, though, I think does use Unix pipes?