[9.3] Sieges: If one or more advancing opponents start the
Game Turn in their #1 Box, they besiege Constantinople.
For each opponent besieging Constantinople, lose one
Development Resource of your choice. The besieging
armies then attack the Walls of Constantinople.
Since "advancing" only applies during the Opponent phase this is already described correctly in the rules.
I agree that the admin loss rules disagree with the admin board.
Losing the Game: The game ends in defeat if the last wall
of Constantinople is destroyed by a besieging opponent or
either a siege or an event card requires a reduction in a
resource already in the #0 box.
This should be updated to "#1" box.