What part of my statement did you misread? Departments generally hand out TAships. RAships come from individual faculty members. So maybe the department reserves most or all TA positions for PhD students. Whether or not an individual gets an RA is the choice of the faculty member with the money.
University research groups are basically like small businesses. Faculty members have pools of grant money and are largely free to hire whoever they want with that money, and each professor runs their own group in their own way. Some flat out will not hire MS students with grant money. Some will. Either way, the department doesn’t have all those answers on their webpage unless they have some department-wide policy about it, and not many do. They’d have a hard time attracting and keeping faculty if they hamstrung them too much like that.