Seeing as he wrote the first version, was involved in the updates, and spends a lot of time promoting GPL, I would assume his views have a large influence in how it is used and perceived. GPL mentions software quite a few times and the preamble states "licenses for most software and other practical works". As I mentioned above, Stallman does not consider art as a practical work.
However, I am not sure how a judge or a lawyer would interpret the word practical work.
What does Stallman or his views have to do with it? The GPL is a document that is interpreted by judges and juries, not by Stallman.
The text of the GPL itself makes no distinction between software or other things that can be copyrighted. GPLv3 even changes its language to make it clearer that it can be applied to non-software things. For example, it defines "source code" as "the preferred form of the work for making modifications to it". What this actually means is up to the aforementioned judges and juries, but for a movie, it's conceivable that the preferred source for modification is indeed the 3d models, the original reels, and so forth.