No its a simple matter of branding. Kleenex is a brand owned by Kimberly Clark, which also owns the TP brand Cottonelle. No reason to compete against yourself unless you're trying to make another brand look good by comparison.

Theres also the fact that the Kleenex brand in the US is extremely closely tied to facial tissues that its basically synonymous. Making a Kleenex TP would dilute that reputation.