If the OS can't see the RAM, then the OS provided ramdisk can't use it either.
But in this case, the use-case for using a ramdisk for a PS scratch disk came from using an A23-aware patched version of System 5.x/6.x with a version of Photoshop that was not A23 aware. AFAIK This was a VERY tiny window around PS1.0 and possibly PS2.0, by the time of PowerPC and System 7.5+ (which this user had), there was very definitely absolutely no advantage to partitioning the RAM away from programs.
At a guess, someone had told them to do it this way in the era of the early Mac IIs and such, but they hadn't grasped the 'why'
But in this case, the use-case for using a ramdisk for a PS scratch disk came from using an A23-aware patched version of System 5.x/6.x with a version of Photoshop that was not A23 aware. AFAIK This was a VERY tiny window around PS1.0 and possibly PS2.0, by the time of PowerPC and System 7.5+ (which this user had), there was very definitely absolutely no advantage to partitioning the RAM away from programs.
At a guess, someone had told them to do it this way in the era of the early Mac IIs and such, but they hadn't grasped the 'why'