No according to the Gloucester cattle society they are a dual purpose breed & there are many traditional dual - purpose breeds (e.g for beef & dairy) mentioned above which include the Longhorns, Shorthorns, Gloucesters & Irish Moiled.
I think for a small starter herd I'd be tempted to go with 3 Irish moiled & 3 Gloucester cows in calf - & have them Artificially inseminated for a few years, so I could breed pure unrelated animals & sell off or slaughter excess bull calves as beef cattle before 32 months, & Heifer calves could stay in the herd if they make the grade, or go for slaughter as beef animals again or be used in the main herd. That way 2 small herds can gradually be built up before introducing any Bulls - so their defo 2 breeds to look into x