I read the original conditions as listed by the OP and basically came the same conclusion as that outlined in the response from the hotel.."double room" being the optimal phrase.
When booking on the SPG or any site listing European hotels one always to pay attention the type of room and/or number of occupants and read carefully into the catcgh phrases.
If there is any doubt make a test booking with one or two occupants.
I must say I do find it surprising that a member based in Europe claims to have blindsided by this turn of events.
mike