Quick answer to your question would be that I absolutely believe this is real due to spending a ton of time investigating the issue to be absolutely sure who I should back up on this before I do, while I admit there is no 100% hard proof, especially with DDoS.
Now to the long part:
About GiG I am absolutely sure because having this many tiny details in GiG exactly the same as in D&D just mathematically impossible. Weapon attack patterns, most skills, core mechanics, same items that are just renamed like "Rapier dagger" with the same rondel model (wtf), the exact same combo cursor ffs, too many tiniest stuff is absolutely the same as D&D which leaves no real room to chance, even considering Unreal Engine Store. Somehow especially that relates to the stuff that was in D&D from the start. GiG is visually not bad, but some game mechanics are so bad that it's almost like someone left them with all the visuals and game design documents, but no understanding of the key mechanics of the game. Nexon's closed P3 project footage I saw somehow had absolutely the same look GiG has (sterile anime'ish style) and D&D has not, due to most P3 visual assets being left to Nexon. An absolutely anonymous studio without any public presence whatsoever (Flame Dragon/The Fool's Studio) popping out of nowhere and making a game looking like this into playtest so quick after their competitor succeeded is a huge feat. Almost like they plenty of something to work with. Coincidentally Nexon while being South Korean also has a big presence in China where The Fool's Studio is based, but of course I was unable to track a 100% clear paper trail.
About DDoS as I said I have no possible way of having hard proof, only assumptions based on Nexon having both ample resources and the biggest motive among everyone else to do that, especially after losing US court. Coincidentally that's about time IM started to have major problems with their hardware, while earlier playtests were perfectly fine.