Hot on the heels of NVIDIA G-SYNC, AMD demonstrated FreeSync, something more easily done with laptop controllers (which can dynamically change refresh rate, but for power saving purposes).
To bring FreeSync to desktop monitors, AMD applied for a DisplayPort 1.2a Specification Change Request, according to this hardware.fr article
(Article is in French).
“Benefits as a result of changes
This enables the ability for external DisplayPort to take advantage of the option to ignore MSA timing parameter and have the sink slave to source timing to realize per frame dynamic refresh rate.”