In any case, it was revealed many actors in that room learned of their character deaths prior to the end of that table read, and while not everyone may have stuck around for the very end, Glen specifically noted to Indian Express he’s a fan of the show.
That said, there’s some reason to doubt that Iain Glen is in the Game of Thrones finale, despite having read the script for it.
So wouldn’t any real fan of the show stick around to see what happens, regardless of whether or not their character was still in the picture?