Amsterdam is a different example because there are 5 other runways besides 18R/36L, so should one become closed for whatever reason, there are still plenty of other options available. I envision it being a major incident to leave 36L as the only landing runway or 18R as the only runway for departures. Which if were the case, would most certainly result in the closure of Schiphol to movements anyways.
Yes, the cost is most likely prohibitive to extend the taxiway at EGCC now, and I agree that money is better spent elsewhere at the airport. But I still believe it would have made sense to have constructed it at the same time as the construction of runway 2, especially considering how much it would have been utilised in the past couple of years.