In this case Caligola(1979), The Pornographer(2001), Antichrist(2009), Nymphomaniac(2013) are not "explicit mainstream", because all unsimulated sex scenes in in these movies performed by a professional porn actresses (in Trier's films using CGI).
"All about Anna" is "porn for women", like others productions from Innocent Pictures such as Constance (1998), Pink Prison (1999). Constance was the first hardcore pornographic film ever to have been produced by an established mainstream film studio. Katja Kean who starred in this film is a Danish former pornographic actress, businesswoman, actress, singer, author. In this case Constance is "explicit mainstream".
So it's not that simple, my friend.
Yes, any scenes in a mainstream film that includes sex acts performed by professional porn actors doesn't count as explicit mainstream...
The problem here that you define by type of the film while I define based on who actually performed the sex scenes.
If the mainstream has unstimulated sex scenes performed by porn actors then the film is explicit but the scenes are just regular porn scenes inserted in a mainstream...
Let me ask you as a member of this forum, if you see a porn actress in a mainstream movie performing as usual! Is this going to be exciting or appealing to you?? What is the difference ?? Now look at something like 9 Songs for instance, it's almost porn but the main difference is that Margo Stilley is not a porn star, this why everyone knows this film..
Imagine if we replace her and the actor too with 2 porn stars, will people care for this movie as much??
As for "porn for women", porn is porn even with artistic touche and some kind of a storyline! The main factor remain the same who is performing the sex scenes?
If you remember in Brazil they had this TV actress and model called Laila Lopes she made 2 or 3 porn movies and it was pure porn but everywhere you will find her scenes from these movies under mainstream or star scandals because even though it was porn but she was a mian stream actress.
Anyways I don't mean to upset anyone just expressing what I believe ...
Have a nice day...