Hi Josué,
This plot of "T_int" shows the distribution of potential phase unwrapping errors: pixels with non-zero T_int values. In my 2019 paper, the multiple peaks are from multiple islands: except for Isabela island where the reference point is, the other two islands (Fernandina and Santiago) have unwrapping errors, more specifically "coherent" unwrapping errors, a.k.a., pixels within each of the two islands share the same unwrapping errors and T_int value, thus, causing the peaks in the histogram plot on the right.
As in your case, there is no peak with T_int > 0, which is good news and means there is no coherence unwrapping errors in your dataset.
Cheers,
Yunjun