Please, for the love of all that is good, never compare any aspect of Brawl to Guilty Gear, or any other fighter for that matter. Melee, the techiest game in the series, pales in comparison.
There's no misconception here. I've said that I can do wavebouncing without the c-stick. It's not hard. However, wavebouncing is more integral to my play than the downsmash is (In fact, I don't use it at all, as there are rarely ever openings to use it, at least with my playstyle and the playstyales of those I play), and thus doing that more easily is higher on my priority list than c-stick to smash is. Combined with the fact that her other smashes aren't really that good...
Also, wavebouncing the up-B is a good bit harder on the analog stick than it is on the c-stick, and I use that for the bounce-up-and-back (Yes, you get the extra height ALL the time if you WB it).