I don’t see allegorical interpretation in the sense that it was merely a vision to explain the fulfillment of the law and the prophesy, sort of like when Jesus spoke of sheep and gates there was no need for actual sheep and corrals for Him to say that.
When they do note is that Moses and Elijah represent a wider communion of Hebrew saints. But I don’t see any dispute that they are real Moses and real Elijah.
The fact that Moses was still in his tomb at the time does not bother these commentators. This can only be if Peter, John, and James saw the future, — but it was real future, not an allegory of the future.
” But I don’t see any dispute that they are real Moses and real Elijah.”
Peter confirms that.
2 Pet. 1:17-18, “For he received from God the Father honour and glory, when there came such a voice to him from the excellent glory, This is my beloved Son, in whom I am well pleased. And this voice which came from heaven we heard, when we were with him in the holy mount.”
Interesting proposition. In other words, they were transprted in time (into the future) and then returned? Time travel? Hmmmm.