
I think the thing about the price changes is two fold - we don't know the full algorithm (which some think is unfair but is a different issue) and most of us (myself included) aren't involved enough with monitoring what we do know about it to understand if price changes look in line with current expectations or are actually unusual and out of line with what we know.
I glance at FPLS every so often and I understand the basics, but the advanced nuances are not something I've studied, so when something odd (to my casual experience of price changes) occurs then I can't tell the difference between manual intervention and my lack of knowledge in the algorithm - any sufficiently advanced technology is indistinguishable from magic - as Arthur C Clarke put it.
Which is why I am personally extremely thankful for the experts like Nigel who do live this stuff day-to-day and whose words on the subject should be given appropriately large weight. They can distinguish the magic, at least to a greater degree than I can.