Is ballast resistor failure a myth?

They definately fail. Usually due to the newer parts and also leaving the key in the run position and engine off overheats both. Also you should have the ballast resistor that is supposed to be in the matched system. Most replacements are not the right values. JFYI
ecu III.png

Same on a point system 90% of them are .5-.6 ohm not one ohm. FSM has the specs for them

I have always thought of ballasts like a safety device sort of like a fusable link for mis matched components.

kind of sort of