Mercy could not slingshot immediately after her rework
While there are many other issues with the Overwatch Classic Mercy that I won't get into here, one criticism I keep seeing is the lack of slingshot. She could not slingshot on the patch of the game this is recreating.
This patch is recreating the patch that Mercy got reworked, so the rez refresh on valk and cooldown lowered to 10 seconds during it. This is the September 19th 2017 patch (also the one that added micro missiles for dva).
One month after this patch, October 17th 2017, they nerfed mercy by removing the rez cooldown refresh and reduction, giving her a second charge instead. As compensation for this nerf, they made it so "Players can now glide past a targeted ally using the jump key". This is the slingshot OW1 mercy had, that then was used for the old superjump.
It's ok to be annoyed at her implementation (don't blame the devs tho, that's cringe), but lack of slingshot is accurate.