7100 = consumer product
72xx = prosumer product
Its really as simple as that. The providers were given the ability to develop new themes and test them with the OS. If they were to release a theme development tool, and someone on here developed a theme for the handhelds, I wouldn't install it on mine - stability is key.
Some themes have been reported as slower than others with the provider-developed themes, so I can only imagine what it'd be like if one of you all were to obtain that ability...