Why is the SETI survey limited to only Red Dwarf Stars?
Sun-like yellow dwarf stars are generally thought to be the best places for intelligent life to develop, if only because 100% of known life is in orbit about a yellow dwarf.  Larger, brighter stars don't last long enough for intelligence to evolve and red dwarf stars were thought to be too prone to solar flares.
However yellow dwarf stars are relatively rare, and the nearby ones have already been investigated.  Red dwarfs are far more common and so there are far more red dwarf stars in our neighbourhood, and perhaps solar flares are not as much of a problem as we previously thought.  So current investigations are focussing on those red-dwarfs that had previously been excluded.