Double Lug?

The main service panel is outside. Aluminum conductors supply 1st remote distribution panel. Copper wire supplies 2nd RDP. The neutral conductor from the service main (aluminum) and the neutral conductor for 2nd RDP (copper) are lugged together. This is a pic of 1st RDP. What are your thoughts on this? Also, what if they were both of the same material?

The material is immaterial, that lug is only listed for one conductor.

Thank you Robert!