As a brief summary of the last few days of insanity,
Sean said that if you organized everyone to be in a centralized spot (ie the center of the galaxy which is the final goal for all players), you would still see quite a few less people than you'd expect because it's not an MMO by design. This, alongside the comparison to journey, and Sean's description of the player as a "walking lobby", made it seem as if game was using instances, most likely based on proximity. He always maintained that the only way to see what you looked like was to bump into another player.
At no point did he ever imply that players flat out could not interact at all. At most, he always deferred to the likelihood of this happening as a reason not to freak out about it. Enjoy the game as is, if it happens, it happens, etc
He underestimated the tenacity of online gamers, as most game creators do. Watching someone turn your 40 hour cinematic experience into a 3 hour speedrun or stress testing the physical limits of your open world or exploiting your loot/craft/drop systems are usual things that happen.
Saying that you didn't bother mentioning that you removed a feature (or hadn't yet patched in a feature, which is obviously still a possibility) because you didn't think anyone would notice yet is still being a bit naughty with language. Part of having a good consumer relationship is being able to manage expectations and level with people when your vision exceeds your grasp, or when technical difficulties are on your end instead of the users'. Having day one server problems isn't unusual. Days of radio silence on whether a mode is even in the game, is.