Danuser Skinner: "Yes!"
Player: "May I see this plan?"
DanSkinner: *looks at Sylvanas* "No."
I assume it's because people are assuming the mention of Argus proves the Titan was connected to the Arbiter's deactivation in someway and is somehow confirming he was involved with the red thing from that one cinematic that struck the Arbiter. I mean they are likely referring to the Titan moreso than the Planet as they weren't part of the Legion when Sargeras decided to recruit the Eredar and it's a possibility they that had some role in preparing the Titan soul later on when they 'forced' to join (despite Antorus showing us that the Sayaad were tasked with dominating the other titans). Though I'm impressed that the writers are doubling down on how all these other failed plans with clear goals at the time were all actually "steps forward in this ancient master plan which we totally have been following all this time and if you don't think about it totally makes sense that our goals and motivations don't make any sense".