If the cone is orthogonally adjacent to the point of origin, you’ll have one more token to place in the row; place it on one end or the other of the row you just created (you don’t have to pick the side chosen in diagram 2.5).

Why do you think this clarification was necessary in XGTE? From what I read above, this seems already implied here: "Starting with a square adjacent to the cone’s point of origin, place one token. The square can be orthogonally or diagonally adjacent to the point of origin. In every row beyond that one, place as many tokens as you placed in the previous row, plus one more token. Place this row’s tokens so that their squares each share a side with a square in the previous row."

Thank you in advance to anyone that can shed some light on this.

If the cone is orthogonal, it's not possible to place N + 1 tokens in the next row and have them all share a side with the N tokens from the previous row. There's always going to be one token left over that can't be placed next to the previous row, so the rules need to address where it should be placed.