IMO, solid rods aren't doing anything for ya in an antenna but adding to the mechanical
loading, making it heavier than it needs to be.
RF current is travelling on the outside of the conductor, Skin effect remember.
It may be that they used solid conductor due to how it is assembled??
Doubt that it would have anything to do with the rf design though.
DB4E/VHF Yagi rotor FM Bandstop ap-8700 preamp 4way split LG lcd.