"Tolkien was among the pioneers of the genre that we would now call fantasy writing. In particular, his stories – together with those of C. S. Lewis — were among the first to establish the convention of an alternative world or universe as the setting for speculative fiction."-From Wikipedia's article on "On Fairy Stories"
I thought instead of Howard and then Burroughs when I first saw this, although the alternative world trope is as old as myth and was already greying when Homer smote 'is bloomin' lyre. This excerpt is pure narrative, complete with erasure of previous works in the field and references to speculative fiction instead of science fiction or fantasy. It ignores the fact that Narnia, the Space trilogy, and Middle-Earth all had bridges to the real Earth of the time, whether directly through wardrobes and rockets, or indirectly, through history. It also ignores that stories with a bridge to Earth or Earth's history are still common after Tolkien and Lewis, as can be seen in Amber, Thomas Covenant, Shannara, and even the Wheel of Time. The only way for the excerpt to hold true is if the writer conflates epic fantasy with the modern fantasy genre, despite the fact that Lewis's Space trilogy is in the tradition of Burroughs's works.