This functionality has been rolled out (shipping) for the past year. From the blog post:
"This was made possible by the phased rollout of the GSP driver architecture over the past year, designed to make the transition easy for NVIDIA customers.
https://download.nvidia.com/XFree86/Linux-x86_64/510.39.01/R..."
And further, the GSP driver arch depends on the GSP controller available on Turing and later GPU's. Per wikipedia Turing was unveiled in 2018, so I guess design work was started several years prior to that unveiling. Not saying the decision to open source the driver was made back in 2015(?) or so, but the wheels were set in motion that eventually enabled the open source decision a long time ago.
