I think that has a lot to do with it. And again, what'd be more annoying? "Terra, I missed you!" or "Terra! Aqua! Ven! I missed you!"?
The former, of course, is preferable by leaps and bounds, before we even begin lining up the hit counts.
My problem with this is that in Days, it didn't feel quite that polar. I guess it had a lot to do with Days' timespan, letting all the different 'personalities' progress at a similar pace whereas in BBS, the Disney worlds were all lax and then BAM. Never once letting the characters progress properly through the Disney worlds into their next plot world persona.
KH1 managed to do that.
Nomura: what is this I don't even-
I think he should just stick to the character orientation. KH1 was largely focused around Sora and Riku's conflict with Kairi serving as a catalyst. In the background you had Sora's developing relationship with Donald and Goofy, and Maleficent dragging Riku deeper into the Darkness.
In CoM you had Sora chasing Namine at full speed with Repliku serving a Riku replacement to partially recreate KH1's success, and Reverse Rebirth was one big character development for Riku that lacked any substantial plot to distract us.
Days too followed more closely to this. While exaggerating at times, it kept its focus around a selected number of characters instead of losing his mind trying to keep track of everyone.
BBS also had this in a way. You had three story lines but you SAW those story lines because you played the other scenarios, and each character had its defined role - even Aqua, whose role WAS to watch it all fall apart around her.
In KH2, he had a ridiculous number of characters who were doing things elsewhere. The problem was that you had Mickey and Riku and Namine and Diz, and the Organization. You effectively had protagonists and antagonists and Sora, the series' main, belonged to neither group. He was playing hide and seek in Hollow Bastion and then Light Cycling with Tron. You had PLOT when he focused around a character who had no direct relation to that. In KH1, he was responsive to what Riku did. In CoM, he was a direct pawn - they wanted to mess with his mind and Heart and Memories. But in KH2 they were these god-like entities, shaping Sora's reality rather than Sora himself and that made Sora, the playable protagonist, basically redundant. And that's where KH2 crashed and burned.
The Prologue? Splendid, a mini-cosmos of CoM revolving around Roxas. TWTNW? Sora actually mattered because he met Kairi and Riku and it was back to character orientation. Now let's have Xemnas give us an excuse for more bonding and SoRikuness and we're all set.
But there was no substance between those two, sans MAYBE Hollow Bastion/Space Paranoids.
Which is again why I stress the character orientation's importance over the plot's. CoM? SoNami implications as far as I'm concerned. She was warning him in half the worlds and the other half foreshadowed their story. Days? Roxas and Xion learning stuff.
KH1? Either you had Sora and Riku interact, or Sora, Donald and Goofy's relationship further explored. The worlds that were "plot" were few and are, ironically one of the most redundant in the game - being Halloween Town (what IS a Heart?) and Atlantica (the whole Keyblade legend thingie).
KH2 didn't have characters to use like that, only SDG. Which might ironically explain why Kairi was dragged in - to keep more players in the game by also introducing Axel back which in turn gave us Roxas and Sora's conclusion.