yes it clearly says that on Sony's information about Supersampling.. they tell you EXACTLY what it does.

https://blog.us.playstation.com/2018/02/06/new-features-coming-to-ps4-in-system-software-5-50/

Supersampling Mode on PS4 Pro "PS4 Pro users will see a new ‘supersampling mode’ under Settings, which enables those with HDTVs (i.e., 1080p or less) to enjoy an enhanced visual experience when playing some PS4 games. With supersampling mode, games that render to a higher resolution when connected to a 4K TV will downscale to match the HDTV – allowing PS4 Pro owners to leverage the benefits of an image clarity boost even if they don’t own a 4K TV. Certain games already have ‘supersampling’ benefits as part of their ‘PS4 Pro Enhanced’ feature set, but this new mode can enhance the experience for those games that don’t already have the feature. Because PS4 Pro’s added power and modes benefit different games in different ways, please note that certain games’ image clarity may not improve with this new feature."

It's pretty clear as day the way they explain it.