Note that it claims the FDL purpose is for functional work.
... with non-functional parts.
Were that true, then the FDL preamble would be an argument that the FDL is not suitable for applying to invariant sections.
Huh?
I think a level-headed discussion is impossible if you are going to contradict the licence you claim to support. Please stick to the FDL.
I haven't contradicted anything. You are inventing things, and putting words into my mouth.