DT is not delivering. They already are far behind schedule for the 24M homes they promised to pass with 100 megabit service. They also reduced the minimum speed to 50 megabits and do not even guarantee that speed. They hide behind almost meaningless "up to" figures; America now requires "typical speeds" and Britain wants to do likewise. DT has given us no reason to believe even a quarter of the vectored lines will deliver 100 megabits.
This is a financial, not a technical problem. The G.vector they are using provides 100 megabits to many in Belgium and 80 megabits to most. The technology is generally working fine, although DT has cut some corners. It's possible DT's engineers misestimated what the speeds would be. It's also possible that the original claims of 100 megabits were a "politician's truth." More likely, they've cut the numbers of cabinets and the fiber extensions. (DT has excellent engineers who are current with the state of the art. I doubt they made a mistake.)
DT's CEO Höttges' comments would make super-spinner Karl Rove proud.