User blog comment:Xilinoc/Ch. 555 - THE HERO/@comment-16214733-20131031162101/@comment-1268838-20131101182201

Frankly, I'm a little glad that he's mixing it up a little here. It's all well and good to wait until you get your ass kicked before releasing your true power, whether it be Bankai, Resurreccion, or whatever, when it happens fight after fight after fight, it gets a little repetitive. Here, we instead have everyone just popping out their wings at once. Not to mention that asides from appearance, Volstandig just seems to be a generic all-around power-up - there is no drama around them suddenly gaining a handful of new abilities, the ones they already have are just made stronger.

As for why they just stood around watching them transform... well, asides from their apparent surprise and shock (and us not knowing exactly how long the transformation took in real-time), it's just an age-old manga trope that I can't even bother to defend.