Polymorph and Size in DnD 3.5

I recently looked over the polymorph spell chain for Dungeons and Dragons 3.5 (Alter Self -> Polymorph -> Shapechange) while reading suggestions on forums for what to turn in to with the spell, and I found something that confused me.

Alter Self contains the line: "The new form must be within one size category of your normal size." Polymorph says it functions like Alter Self, except where otherwise noted. The only thing Polymorph says about Size is the line: "You can’t cause a subject to assume a form smaller than Fine", which doesn’t seem like it would invalidate the Alter Self clause. Shapechange, on the other hand, specifically clarifies that whatever you turn into can be anywhere from Fine to Colossal in size, which seems like it would overrule the Alter Self clause.

This is confusing to me because when reading over forums and suggestions, people are suggesting that you use Polymorph to turn into Huge sized creatures, such as Hydras. Is there an errata or clarification that I was unable to find that would allow this? Rules as written, it seems as though this is explicitly not allowed until you acquire Shapechange (unless you’re a naturally Large sized creature, since size changing spells do not stack together as per the spell Enlarge Person).

I’m willing to accept that this is just an example of the polymorph chain of spells being poorly written, as the Alter Self clause: "A body with extra limbs does not allow you to make more attacks" had to be clarified by Skip Williams to only mean WEAPON attacks in this online post: http://archive.wizards.com/default.asp?x=dnd/rg/20040518a

If there’s some errata or clarification I’m missing, I would love if someone could provide it. Thank you in advance.