Beginning a full attack as a partial action~

[dcollins]

I'd like to point out that "if an action is normally a full-round action, sometimes you can still do it as a partial action, and sometimes to complete it you need to use the start full-round action and complete the action in the following round with another partial action." (PHB, pg. 127) This neatly divides full-round actions into two groups...

No it doesn't. There's nothing in that language that implies it's a strict "either/or" relationship. The full attack action happens to fail both those "sometimes" clauses.

Come on, the "start full-round action" definition is very explicit that it can only be applied to a "miscellaneous full-round action" (PHB p. 127). And of course, you snipped out the last part of the sentence from your quote that refers one to this definition for specifics on the second case.