Their management of award and classes is absurd. T is also a revenue bucket, there are flight with X wide open and T closed, and a few have X closed and T open. T is the cheapest booking class for fares without minimum stays, so pretty much sold out several days before departure, to force business travellers to buy more expensive fares. Moreover, T fares are quite cheap usually, around 100-200 EUR before taxes and surcharges... not a good value for a return trip!