I don't have any information at the moment with which to back up this thought, but the "maybe this was a parable" line seems to have originated solely from those wanting to deny the reality of hell. I have not read in any writings of the pre-higher critical church where this though was entertained. Maybe someone with a little more background in the history of interpretation could make a pronouncement one way or the other, but its source of origin seems to make it a bit suspect as an orthodox interpretation.

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Adam J. Myer
Pulpit Supply for PCA/OPC/URCNA congregations in the spiritual wasteland known as the Pacific NW
Evergreen Presbyterian Church (PCA)
Hinterlands of Oregon

Soli Deo Gloria