Some climbs can be harder in winter if the snowpack is less. So that's the flip side of things. Un-covered brush, un-iced couloirs (Triple Couloirs, for example), un-snowed-in couloirs resulting in rock climbing where there usually is none, un-bridged crevasses, gaping schrunds, objective rockfall hazards where rocks are usually held fast by winter snow and ice, etc. etc.
So as Fox said, it should only ever be judged by dates alone. An FWA is an FWA. Winter conditions are winter conditions. The two are separately defined but most often do overlap.