As far as we know the Sunny Boy/Sunny Island combo is the only AC coupled system that provides this feature. The benefit is not only in overall product quality, but the unique feature that reduces battery bank cycling.
When you lose grid with an AC coupled system, the Sunny Island can change the frequency of power coming from the solar array to match the loads (throttle). The benefit is that batteries only turn on when the array is not able to supply the load requirements, or at night.
Other AC coupled systems will shut down the solar array when the house cannot consume the output of the solar array. At that point, the battery bank turns on and supports the load until it reaches a certain DOD. The array is turned back on until a full state of charge is reached, and the process repeats itself.
Excessive cycling of batteries is prevented by the SB/SI combo. Recently, Schneider Electric has introduced a similar solution with the Context XW+, and the jury is still out on reliability because they have not been field installed for very long.