[weinzierl]

Here is my whole comment. Somehow the last part I posted in an edit magically disappeared:

That is true but not whole story. I believe when people talk about PBR Textures they most often use PBR synonymously to "Principled Shader", "BSDF Shader" or "Disney Shader" (all meaning roughly the same thing).

When it comes to 3D data, exchanging geometry has been possible for a long time. Essentially and most of the time we just use triangles as the lowest common denominator. Most of the difficulties are more or less accidental complexity because of different formats.

When it comes to textures this was not possible for a long time, because every renderer used its own algorithm and they all had different parameters. There was no lowest common denominator.

When Disney invented BSDF it allowed the exchange of realistic materials for the first time. The "format" won and is what is sold or given away as "PBR-Textures".j