As much as it pains me to say it, Dave is right.

The first video you linked to Alex, the shaft wasn't bolted either side of the bulkheads (namely due to time and lack of facilities), and in the second video, the shaft was bolted using M6 bolts. M6 vs NST, it's obvious who is going to come out on top
It didn't help that back then, I thought that the standard hole size prior to tapping was 0.5mm less than the thread you were going to cut, regardless of how big or how small the hole was. Got it right this year, though typically didn't face any horizontals.

It's also worth pointing out that the drum on the 2011 and 2014 versions didn't span the entire width of the bulkheads, which meant there were gaps that were perfect for NST's bar to bite into and throw the bulkheads apart (the 15mm ali came off worse in 2014 than the 16mm Nylon did in 2011) but again, this year saw the drum span the entire width, meaning that any horizontals are more likely to catch the drum rather than the bulkheads.

Moral of the story is, wait for someone else to perfect your design and then copy the living daylights out of it.