You’re welcome, here’s the NEC reference for anyone who’s interested. 250.24(A)(1) generally states that the GEC connection can be made at any point up to where the neutral conductor terminates. The EGC bus in the photo is after that point so the GEC cannot land there unless it meets 250.24(A)(4). Since there is a green screw as the main bonding jumper the GEC terminating on the EGC bus does not meet the requirements of 250.24(A)(4) so it cannot terminate there.
250.24 Grounding Service-Supplied Alternating-Current Systems.
(A) System Grounding Connections. A premises wiring system supplied by a grounded ac service shall have a grounding electrode conductor connected to the grounded service conductor, at each service, in accordance with 250.24(A)(1) through (A)(5).
(1) General. The grounding electrode conductor connection shall be made at any accessible point from the load end of the overhead service conductors, service drop, underground service conductors, or service lateral to, including the terminal or bus to which the grounded service conductor is connected at the service disconnecting means.
(4) Main Bonding Jumper as Wire or Busbar. Where the main bonding jumper specified in 250.28 is a wire or busbar and is installed from the grounded conductor terminal bar or bus to the equipment grounding terminal bar or bus in the service equipment, the grounding electrode conductor shall be permitted to be connected to the equipment grounding terminal, bar, or bus to which the main bonding jumper is connected.