It's just impossible to impliment Arcsys netcode onto something that is widely incomptable not just gameplay wise, but how they were both built.
There is truth in this statement, I would advise people to not keep asking SNKP to use netcode that isn't their own. 3rd Strike is a prime example, an implementation of GGPO that is worse than most.
As for SNKP owning GSS, now....that is unlikely, but whatever the situation is, netcode must be made to work. Although it befuddled me to no end why SNKP would ever conceal such a fact, more likely it's ONE OF THEIR HIGHER-UPS EXECUTIVE who owned GSS not the company itself. And thus perhaps, just PERHAPS, that he/she deliberately stifled netcode development in order to keep SNKP using the GSS. It's not that far of a stretch, things like this happened all the time: say Kei Yamamoto wanted to use better netcode, be it from their NGBC or GGPO or whatever, then comes order from the board "nope, use GSS". But again, it's unlikely...they fired Maasaki Kukino over KOF XII right? well he resigned actually, but that still proved (at least marginally) that SNKP still cared about their game quality, and willing to spend money and pay to fix the failing. Remember, SNKP ran a huge risk hiring new director and crews for making KOF XIII. Which as we all remember, cannot afford to fail). Luckily though, this Kei Yamamoto guy is an ace, he knew what fans wanted and he gets the job done.
I predict a good year ahead with Kei in the helm, now....if we could only get T.Nishiyama back....he would revive Garou in a flash. Guys, remember how we complain about SNK not being the same anymore? well it literally isn't the same...90% of SNK game in the 90's are produced by T.Nishiyama, while SNKP has had Falcoon, Maasaki Kukino and now Kei. Not to mention one of their exec producer from KOF 2003 all the way to KOF XIII is Soimen (a mystery man still using old-time weird pseudonym like in the Neo-Geo days).