PSF and ATF is very close, both are hydraulic fluids

However, the strong clensing agent required in atf does not exist in psf. when atf is being used for ps, there is a chance that the ps o-rings are getting hardened slightly quicker. If you use psf for atf, you may ruin trans.

Rule of thumb - unless user manual says to use atf for ps, stay with psf for ps. never use psf to trans.