Hiya!! Thank you for the kind words and the awesome questions!!
Yeah that's some of a slew of Typos that are getting fixed in 0.14 ((Soon...ish... probably...))
So two handed parts actually fully break if either one of the slots is broken! ((It's a major tradeoff of these otherwise very powerful weapons)) One of the advantages of Super Robot Helm is you're halving the chance of this happening (and freeing up an arm slot). The reason 2-handed parts spread their text across 2 "parts" is just to make use of the space, it's all meant as one contiguous part. ((Of note though, if it break it only counts as 1 Part Break))
Hope that helped clarify things for you!