[Sunred]

I checked the katakana and I don't think the bad guys should be written as JACK MATTER at all.
It should be JARK MATTER(JARK being a portmanteau of ja-aku and dark, ja-aku means nefarious or demonic) based on how it is written in katakana.
The reason is because "Jack" is commonly written as ジャック, yet the name of the bad guys are written as ジャークマター, and notice how ジャック and ジャーク are not just written differently, but also pronounced differently(subtle but still different).
Thus why I think it should be Jark Matter until Toei says otherwise.