Let me put it this way, looking at the steel versions with their huge L/D, tiny SA/D in low aspect rigs, small Bal/D and huge amounts of wetted surface, I can't imagine that they can possible sail well. I have never heard anyone claim that the smaller Roberts designs reportedly sailed well but as you have said perhaps some of the poor sailing ability may be about execution. To me these are sailboats for people who don't really want to sail.
I would tend to agree. The only ones I heard about that sailed at the very least "adequately" (which is subjective, to say the least), were the larger models, like the 434.