Really? I've always been under the impression that DT2 was also included there; as adding the ;dt to whatever link you were in did also include feedback left by DT2 members
The depth system says otherwise. The DT members are the only ones selected by the voting. If you were to put ;dt, it simply displays the DefaultTrust up to the depth of 2, as per the default.
If you were to consider only those in the DefaultTrust only, you can only consider DT1. DT2 only exist because you put your trust list depth at 2.