Point blank casts did refund the grapple hook cooldown at one point, but at some point within the last year that changed - Pointblank No Refund GIF by brokenstyli | Gfycat
Proof that it used to refund at one point - fix the grappling hook - YouTube
I still keep tabs on Widow’s bugs and issues, here - Widow Bug/Issue Megathread w/ Video Examples (updated? 25 January 2019)