#2
No, but various brands of "hex-core" strings have been on the market for years... This would likely be just a variation.
The idea sounds good... By making the core wire hexagonal or octagonal, there are little "corners" for the wrapping to bite into.
That's what the advertising copy shows.
However.... Will that really make any substantial difference? I mean, we don't normally see wrapping wire come loose anyway, right? It's the "mass" of the string and wrapping that makes it work... As long as the wrap is good I doubt the shape of the core wire will make any substantive difference.
#3
If you think about it, a hexagon has sharper points than an octagon. So, the hex core should dig into the wrap more than the octagonal core. Jus'sayin'. (Material composition being equal, obviously).