I believe you already…
I believe you already answered your own question. People have reservations for the other non-Foundation series variants. Tesla has always launched product line starting with the highest variant first, then phase in each variant. It only makes sense that the most expensive version would have the lowest number of reservations and is nearly completed there orders for the Foundation Series. Therefore, your new reservation for a Foundation Series jumped the line ahead of the other non-foundation series variant reservations.