spoiler Spikezilla...(spoilers)

[Dragulia 17]

so have i been saying for years that the greed only result into body growth, not actual age
the Spikezilla in the season 2 episode, was nothing more than an oversized greedy baby.

Greed Induced Growth: AKA Honey I Belew up the baby.

[AlbaTross 1,586]

That's what I was thinking, although it was also accompanied by a deepening of Spike's voice and a more mature appearance, both of which are things commonly associated with puberty and beyond.  I think the writers kind of backed the series into a corner here as that particular event was witten back when the lore surrounding dragons wasn't anywhere close to where it's at now.  Smolder mentioned that event is "something different" but didn't mention how it was different.  It's possible that they are two different puberty events, one of which Spike resisted, but I don't know.  

The molt seems more akin to what is commonly seen with 13 year olds, given that Spike got zits and started to smell, and then ultimately experienced a change in his body which in this case culminated in the growth of wings.  If your theory is correct then maybe most dragons are more equipped to survive the molt in spite of predators lurking everywhere as the average dragon could be massive too.  I mean, dinosaurs were massive which helped a lot against bird predators (who were also dinosaurs, but whatever).  That still doesn't explain why there are dragons like Garble, Ember and Smolder who are bigger than Spike but proportionately only to the extent that individuals in their mid teens or older often are in comparison to a small child.  It seems unlikely that the disparity between, say, Ember and her dad in terms of size will ever be explained, so we can argue about that for an eternity, along with whether what Spike experienced in season 2 was indeed purely about size.