It is -I can't imagine why Subaru would use a different parking brake between the nearly identical platforms vs simply a larger disc that fits their standard parking brake unit which is probably the very same unit used across all their models except maybe the Tribeca.
I bet it is identical
R180 / DCCD cars (except '95 STi Ra) tend to have the Large parking brake / BIG rear axles combos but all others (? tribeca) have the same small parking brake.
I did the 2005 LGT (2006-2007 WRX rear rotor) conversion on my 2003 Legacy L-SE everything was bolt-on, BUT you have to use 2005+ LGT calipers / caliper brackets.