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That is what I assumed, otherwise it is just a simple capacitor coupling de al like in millions of devices.
Not an OP AMP, but they use some sort of thing like this in some Sony and o ther audio amps using VFET outputs. With those, since they are depletion mo de, you cannot use a dim bulb or variac on them or it will blow the outputs .
There are other examples of DC level shifting all over the place, and most are simple. In most, it is simply AC coupling and the stage receiving the s ignal resets the level to whatever it likes.
Actually, now that I think about it, Jim Thompson is right. My little drawi ng, the DC will not track at one to one. Well it could if the resistance va lues are chosen right - I THINK. If the desired DC offset is constant, it i s not hard to make the DC gain unity as well. But if he wants to vary it at will it gets a bit more complicated.
But I assume he was not looking for "Put a capacitor there".