The recommended values added to the manual are based on recommendations for "diffuse mean path" from pixar's renderman (renderman.pixar.com) documentation. I believe those values are also behind the various presets in the FireFly Scatter node (Lighting > Special > Scatter)

During P13 development a lot of work was put into making sure that the various SSS nodes achieved consistent results with similar settings. The settings were added to the manual during all that testing, so yes, it is new information that was added for the P13 docs..

As regards to the "Scaling" value for Subsurface Scattering ... 

For Physical Surface Node, it would be the "ScatterScale" setting (fourth from bottom)

For Principled BSDF node, it would be the "Subsurface" value (fourth from the top)