Hello, @Bruno.Nguyen
If I am not mistaken, the larger value of thrust reported in the IEA15MW report includes not only the aerodynamic load, but also the weight of the rotor (similar to what is explained in this post NREL 5-MW reference turbine - CP, CQ, CT Coefficients - #33 by Jason.Jonkman), while the one from DTU is only the aerodynamic force. You can check that the difference between these two values is the weight of the rotor times the sine of the tilt angle.
BR,
Lucas