Grounding and STP drain design questions

[Ferrous Bueller]

I am studying the S.E.X. manual's wiring diagram and have some novice grounding questions.

There appears to be a copper star-ground scheme used for part of the design, but all of the STP drains (except for 1) do not use the copper star grounding scheme.  Is there any reason for this?

L3, L8, L13, L18 and L23 rely on the aluminum plate for the ground and do not have individual copper ground wires going back to the safety ground lug.  Is there a reason for this (e.g. higher resistance to ground)?

Sorry for the novice questions.

TIA

[Doc B.]

Great username. The drain wires are for shielding. They are effectively part of the chassis ground plane and thus they are connected directly to it.