I think that's pretty much what happens, however the Shanklin to Ryde Pier Head train has 4 minute turnarounds at each end.
To fit in with it at the passing place, the other one isn't exactly half-hour opposite, and can only go as far as Esplanade, having a 4 minute turnaround there. It has a longer, 10 minute turnaround at Shanklin.
In short, there isn't time for the second train to go to Pier Head and get back to the passing place in time. It has to terminate short at Esplanade.
It all looks an ill thought out mess to this onlooker I'm afraid.