I think you're conflating the dark room where Future Guy appeared that never looked as cool as it did in the pilot with the white void where Trip and T'Pol psychically bickered in their dreams in season 4.
I think he's thinking of the Sphere Builders,
who we did see talking to each other in a white void.
This episode was a lot of fun.
I'm a huge Agent Carter fan, so I really enjoyed Sousa's appearance.
The big robot vs robot fight with Coulson and the Chronicom was cool. Seeing Coulson with actual superpowers is pretty cool.
I think we got even more funny then vs now moments in this one than we did in the first two episodes.
Simmons pretending to be Peggy Carter was pretty good.
I'm looking forward to seeing where they end things with Sousa next week. I could definitely see them taking him with them.
I was thinking earlier today about how I'd want to see the show end. The big thing for me is that I really think Coulson should die one last, true, final death. The show started with Coulson being brought back from the dead, so having him die once and for all would be a perfect way to counter that.
Since Coulson seemed to be setting Daisy up to take over S.H.I.E.L.D., I would love to see Mack step down and for her to take over.
I would love to see Fitz and Simmons married by the end.