The intention of that paragraph is entirely the opposite: At the moment fallback mode is meant to be a fallback mode. When we drop that fallback mode, anyone will be free to develop metacity, gnome-panel and so on as they wish.
If you disagree that fallback mode was a fallback when hardware support was not available: it is called fallback mode; customization was not impossible, but the default obviously had to look like GNOME 3. Various applets were ported during 3.2. Various work still went into it in later versions (ibus).