The word 'secret' is being used differently than usual here. Another weird English thing. He doesn't mean secret as in restricted, kept hidden, etc. but more as in wanting to discover something new -- 'the mysteries within'. Yeah you can look at images etc. but decapping it yourself is always more fun, plus it's cool to actually see the bondwires etc. Until you see them in real life it's hard to appreciate just how amazing ICs really are.
Yes, you could discover the same things by decapping any IC. But I've always wondered what's under the blobs -- it must be interesting to see the bare die with bondwires going directly to pads, instead of inside the plastic packaging that's usually surrounding it.
If you don't understand why someone would want to do this...
there's not really any explaining it.