I think plenty of folks just have a vague understanding of electrical codes and say stuff like that to impress others.
Generally speaking, you're just not supposed to do permanent electrical wiring with extension cords and power strips, especially not for stuff that goes into or through walls. This has nothing to do with plastic - you have plenty of plastic in electrical boxes, outlets, PVC conduit, etc. Cable insulation is plastic too.
The electrical code doesn't want you to put extension cords in the wall mostly to make sure that the connections can't come apart, that the comparatively softer and more delicate wires aren't easily crushed or abraded, and so on.
This project definitely isn't done the way you should do it if you had a real budget dedicated to it. Is it a death trap? Meh, I've seen far worse extension-cord contraptions in US homes.
Two things come to mind: 1) if any arcing occurs, a metal enclosure will shunt to ground and (hopefully) trip a breaker; 2) in the event of an overload, plastic melts which might result in a fire.
Plastic distribution boxes are actually really common in residential installations in Europe, Australia etc. The UK standard has changed to metal now for fire risk but plastic is common around the world.
It’s more the grounding issues and lack of a properly sized circuit breaker to protect the extension cords etc.
The fact that this is the most appealing option is an indication that our electrical system, both equipment and code, are failing to address people’s needs. If you get a quote for a hybrid (on and off grid) system, they’re absolutely unaffordable.
Power distribution centers are not power strips and there's a reason for that
Yes, we are on the cusp of self-pluggable home solar solutions.
No, this is not the way.