It has nothing to do with mysticism, spirituality, or hippy-dippy shit - unless you consider a seed germinating to be spiritual.
Permaculture is a pretty sound set of ideals. The problem it's suffering from at the moment is that it's been turned into a new money-making scheme. Expensive books, courses, presentations, etc.. and most of the material is inadequate as the success of a permaculture site is entirely dependent on local climate and species.
Bingo!
I'm currently living and working at a very nice little project in the south of Spain where one of the terraces has been turned into a "forest garden". Forest Gardens are somewhat totemic in permaculture because one of the 'founders', Bill Mollison, was originally a forestry worker in Tasmania and it was his observation of the complimentary relations between plants in natural eco-systems in the Tasmanian forest that partly led to Permaculture being formalised as a design system. He realised that overall crop yields were much higher per hectare in natural forests than in 'conventional' monocultures - albeit that of course many of these crops weren't of much, or any, benefit to humans.
The Forest Garden then is an attempt to reproduce the 'natural' climax vegetation system (assumed to be a forest) but tweaked towards human-benefitting plants, eg nuts, fruits etc with underplanting of other crops - "stacking" in the jargon, giving much more efficient three-dimensional use of the space. By mimicking the natural vegetation form, less labour is needed to maintain the garden - unproductive plants are crowded out.
Problem: where I am, forest is not the natural climax vegetation. There were never forests here. To keep trees alive, they need to be irrigated regularly (once or twice a week) using acequias (ancient Moorish irrigation lines) that deliver water from a spring. I have to regularly trample over the site opening and closing irrigation channels. Underplanting is a total pain in the arse, I walk all over it every time I irrigate. I used to tread round it but now I can't be bothered, if it's in the damned way I walk on it.
Moral: as you say, observe the local vegetation etc. But this "forest garden" has been planted (and then maintained) for years - even visited by Patrick Whitefield (?sp.) - a bit of a permaculture guru - and given the thumbs up. I really wonder at how this happened - some very un-self-aware cultural imperialism really - "forests are the norm". Well no, not everywhere they aren't, actually a minority of the planet really.
Permaculture is essentially a thoughtful and intelligent design system, but the minute any part of it becomes doctrinal, it's horseshit. Forest Gardens are a great idea where forests are the natural climax vegetation. Anywhere else they are as a daft as turf golf courses in Abu Dabai or any of the other nonsenses of the modern world.