I just tested, open a 2D dwg i TC v21 pp, save as tcw, made a roof, save, then save as dwg with By Default setting in dwg menu, no problem to see the roof in AC Trueviewer 2017, and the explode was not checked by default.
Also no problem to see the "New" dwg in TC when opened there later
V18, V19, V20, V21, 2015/ 16/ 17/ 18 Pro. Platinum
Deluxe V20, V21, 2015/ 16/ 17
Windows 10 Home Premium 64 bit, 32 GB
NVIDIA Geforce GTX 780m, 1 GB