but in practice, PSE is almost exclusively associated with greek when the term is used.

Many GFE providers are fine with COF and/or CIM so to say that they are PSE would be misleading at this point to many clients.

to retire the terms PSE and GFE? Sex with girlfriends can include COF, CIM and Greek, too. Does the overall experience change that much according to what happens in the last 30 seconds? IMO, GFE and PSE are only somewhat meaningful anymore as totally subjective impressions.

They all mean whatever the provider thinks they mean.  Sometimes they mean CIM or Greek, and sometimes they don't.  I've had a provider who advertised open to all fetishes, say no CIM or Greek, when we met.  And one who said fetishes meant she would wear different outfits. That's why you need to read the TER reviews, or need to ask the provider ahead of time.