How pickups work

I was reading another thread and noticed a lot of people here wind their own pickups, so I was interested in what you folks thought about this.

There's an interview/chat online between Seth Lover and Seymour Duncan - two guys I'd say are worth listening to in the pickup world - and Seth says to Seymour (I'm paraphrasing) what people don't realise is the pole magnet is only there to magnetise the string. The string gets magnetism from the pole piece, then the string becomes a magnet. That's then a magnet moving over a coil, and therefore electricity.

So it's NOT, like you often read, the string cutting through some invisible magnetic flux (we've all seen the mushroom diagrams online of magnetic fields). The string is the magnet. You could move the pole piece outside of the coil somewhere else, as long as it magnetises the string....? What if the strings were magnetic out the box? Would the pickup just need a coil?

Any thoughts? Anyone done any tests? Is this common knowledge to pickup winders?