Todos os micro-cabos USB 3.0 usam esse estranho conector duplo na extremidade pequena?
Sim.
USB 3.0 also introduced a new Micro-B cable plug, which consists of a standard USB 1.x/2.0 Micro-B cable plug, with additional 5-pin plug "stacked" on side of it.
That way, USB 3.0 Micro-A host connector preserved its backward compatibility with the USB 1.x/2.0 Micro-B cable plugs.
However, it is not possible to plug a USB 3.0 Micro-B plug into a USB 2.0 Micro-B receptacle, due to a physically larger connector.
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Backward compatibility
USB 3.0 and USB 2.0 (or earlier) Type-A plugs and receptacles are designed to interoperate.
USB 3.0 Type-B receptacles, such as those found on peripheral devices, are larger than in USB 2.0 (or earlier versions), and accept both the larger USB 3.0 Type-B plug and the smaller USB 2.0 (or earlier) Type-B plug. USB 3.0 Type B plugs are larger than USB 2.0 (or earlier) Type-B plugs; therefore, USB 3.0 Type-B plugs cannot be inserted into USB 2.0 (or earlier) Type-B receptacles.
Fonte USB 3.0