tiagra hubs are great
but i dont think they have ever been made with 7 speed casettes
they have cassette bodies that fit 8 9 and 10 speed cassettes
unless these are refurbs and they changed the freehub bodies

also
most 7 speed road bikes had
i think
126 mm spacing for rear hubs
but tiagras
and virtiually all 8 9 10 speed road hubs
have 130mm spacing