Yes, those encrypted macromodels may lack the elements
needed to represent the VCC-VOUT transfer function (as
well as any other paths). SOmebody would have had to
make the effort, unlike transistor-level models which this
would "just fall out of".
Of course being encrypted you don't get to inspect. That's
why.
You might find a schematic made of transistors out there,
some folks make a hobby of that. Not to say, likely. Unless
you happened to pick a popular part that happened to have
such a fan.
Simply, you could set up two DC OP analyses at two
different supply voltages but consistent load and feedback,
and then PSRR is dB20((VOUT2-VOUT1)/(VCC2-VCC1).
You can explain a lack of credible supply driven output
deflection as a lack of macromodeler effort, if challenged.
Doing something about that, though, would slide into reverse
engineering and proprietary SPICE transistor (& passives)
model scrounging.
Might wade into the contrib libs behind LTWiki and see if
any fans left you a bonus...