That's exactly what they say about Iowa's weather as well!
Given the latitude (but completely ignoring altitude), my thought was just that Texas's Winter, such as it is, is comparatively shorter and milder than ours, so the water temperatures wouldn't decline to the levels they do here..and so fish would tend to be more active there during the winter. They are active here as well, but you usually have to drill a hole through 10"-18" of ice to reach them.