Bleach VI: We Want Our Baby Bach Ribs (Aizen pull)

[Morph Bark]

It is possible that when you kill a powerful Hollow, it shatters into all of its component Hollows, which then reform individually in Hueco Mundo.

That could also be true. Which would mean Hollows eating Hollows is actually beneficial to Shinigami, as then they need to defeat less Hollows (plus the stronger ones don't go to the real world as often).