Only that form of the tomb could explain why the Beloved Disciple was originally the first to see and witness the resurrection of the spiritual Christ of Marcion, as opposed to Peter. It was sufficient for him to arrive first and to see inside it, in the pit on the soil, the absence of the body.
While in the Catholic John, the form of the tomb is modified: it is a pit in the rock, so that on the same level Peter could enter inside it first, differently from the Beloved Disciple (despite of the latter being the first to see from outside the tomb), something he couldn't do if the tomb was merely a pit in the soil.
In proto-John the tomb was a pit on the soil, not on the rock
In proto-John the tomb was a pit on the soil, not on the rock
Nihil enim in speciem fallacius est quam prava religio. -Liv. xxxix. 16.