For the longest time yeah, it was the centre interconnection of all major routes though the town centre. If you look on street view you can see the main arteries working out from there to the older parts of the town (ignore west and north neither existed in the 70s.)

I think it will predate the M4 and A417/9 build dates just, 100% predates Thamesdown drive so you didn't have good circular options around the town.