Your reference is correct. Stainless steels are more corrosion resistant than HSLA steel. HSLA steels are in turn more corrosion resistant than carbon steels. Corrosion resistance is a continuum. Chromoly is relatively corrosion resistant.

Reference: http://en.wikipedia.org/wiki/HSLA_steel

"HSLA steels are also more resistant to rust than most carbon steels, due to their lack of pearlite."