If you plan your range circles at a certain TAS, you must also carry the fuel to achieve that TAS, with minimum reserves at landing.
Whether or not the crew elect to fly at that speed is another matter.
If this amount of fuel is not carried then they must fly slower and then by definition could be outside the 120min (or whatever) approval. Remember, an ETOPS requirement is to be within a certain time of an adequate airport, not a certain distance.