Ah, my apologies. I thought you were talking about the Archetype/Class terms that seem to have caused some confusion.
In that case, I think Cactus has the right of it. In the first big magazine article (PCgamer), they mentioned some sort of system that was more free-form than VT2. I think they referred to careers in VT2 being a “crutch” to achieve an idea they had for classes and roles but wanted to do something more elegant and less rigid for DT. Sadly, all my links I had saved to YT read-throughs and such are dead now. I found this wordblog that gives a brief summary but eh . . . better can probably be found. There was also the Edge article, but I don’t know if that one mentioned the theoretical “free-form” system or not.
The next closest thing was this post for the beta tests. You can see he says they will be quite different from the career systems and I recall being distinctly puzzled, because, like a lot of commenters in that thread, I felt it was the exact same as the career system.
There was a lot of speculation on how things exactly went down. We were told this just days before the CBT, then the CBT launched with what could best be described as these sort of patchwork talent UI for very generalized classes. There was no artwork for the talent page at all, just the buttons. By the POB, the page got the stained-glass window background and the talents themselves got overhauled a bit. It all seemed to smell like a bit of a rush job, so the thought was that, as the crunch came and they weren’t managing to balance whatever tree system they had at the time, they reverted to the safe familiarity of the career system to get the game off the ground. They had two plans going forward: continue to develop career system OR attempt to get the original plan to a working state. Fortunately, they chose the second and brought it back to life. At least, that’s the theory.