The stuff about reading the bottom of the porcelain inside the plug I knew about and it was in the link I sent you, more or less, but the timing line? Never heard of that.
What I was a bit surprised about was that he didn't tell you, when fitting a plug, is to always fit it so that the strap is to the outside of the cylinder. TBH it normally does that as plugs are supposed to do that straight out of the box, but it is always worth marking the plug on the outside so you can make sure it is lined up properly.
Nevertheless, interesting.
It makes me want to pull a plug on W's car which is all electroniced up to see if what he says is there on her plugs.