Zeb’s theory is that the bold central grigne is more likely to be successful in doughs with a linseed soaker.
These are Zeb’s beautiful Rye & Linseed.
But it also works in Oat & Honey:
(that was deliberately slashed more to the side – honest) and in Thanksgiving Bread:
– which is heavy with fruit & nuts, and in Black Bean, Jalapeno, etc pictured a few posts down.
Maybe it just works best in fairly heavily loaded doughs. Or maybe it’s like a theory I heard about tequila which is that tequila has a reputation for being more potent and causing more riotous behaviour than other spirits, but maybe that’s because people drink it when they feel like getting arseholed and letting rip. So maybe you only try the spectacular central slash on doughs you sense will take it. Or maybe I just got up too early.
The PArtisan Baker 
I suspect you can probably do these in your sleep Mick!
They only work for me once in a blue moon, and mine were a complete surprise when they came out of the oven – hence my probably erroneous theory, but you know what they say you can’t prove anything, only disprove it, so I think you have neatly squashed my theory, mate!
(tequila is about the only liquor I can drink without getting a blinding headache instantly, there’s a complete irrelevance for you to ponder as well)