While it is true that sex in porn flicks is largely uncovered, this is not what is meant by "Porn Star Experience." At least, this is not how the majority of providers who advertise PSE sessions are intending the term to be heard...
If you see, for example, GFE $300, PSE $400, the extra $100 is for greek, unusual fetishes and/or or role play. A PSE session usually includes all GFE activities (kissing, daty, bbbj) PLUS greek and POSSIBLY cof, cim, or squirting. Also, PSE denotes a different mood than GFE...while GFE sessions may include wine-sipping, cuddling and chatting, PSE sessions are typically characterized by balls-to-the-walls sex, multiple positions, rampant dirty talk.
This is what I have seen to be characteristic of the escort industry. No first-hand knowledge of the porn industry, or of porn stars who also escort.
To make it really easy for you: the most common meaning, when you see it in an ad or on a site: PSE = greek. Simple.