I was worried about that too, but carefully looking at the example showed that it wasn’t necessary. I think the x + 100y requirement is just a simple way to convert a bunch of coordinates to a single number for the purposes of submitting an answer.
I do find it funny how AoC sometimes ties itself in knots explaining a very simple problem like getting an x,y coordinate, while at the same time writing problems where the optimal solution requires prior knowledge such as modulo, quadratic formula, Chinese remainder theorem, graph theory, shortest path algorithm, etc. etc.
