That is my experience, yes.
The FD does indeed appear to withstand heat better than TD but also seems to keep its wax better, wheras TD uses a gel that seems easier to remove with detergent, mechanical scrubbing, and sanding. That said while ive tried painting both, I have not tried casting FD. I dont know if/how the wax may interact with the particular brand of mold you are using so, as always, test first in a pressure chamber after degassing the mold and then inspect to see if a chemical interaction caused bubbles or some other strange effect in the mold.
I have one more data point since the last post which is, I took a FD model, and baked it several times in a toaster oven, wrapped in foil so it didnt get directly radiated by the element. I had suspected the model was holding water, it appears it was actually holding wax. I baked with the oven set to "150" F for about 2 minutes and let the assembly cool. I did this three times. WIth each bake I saw trace amounts of wax collect at the base of the model, or at potential minima, even when I thought it was wax free. I believe the tinny pores of the FD (I have not tried any FUD) hold wax amazingly well. Multiple gentle bakes might get the wax out... but they might also destroy the model. I didnt bother continuing this cycle to get rid of the wax, I gave up. THis wax is also resilient which is why I think sand paper didnt do what I expected. I think I was just smearing wax on the model every time I sanded it with a 400 or 600 grit wet dry. I dont know what solvent one might use to remove the wax that wont attack the plastic.
I also dont know what temperature the oven actually got the model to, so if you try this do it gently for short bursts and make sure the model is in a pocket of air protected from direct radiation with 1 layer of foil. I was using oil free foil but I think normal foil will work just as well. dont wrap the model tight with the foil, just make a mostly closed bubble.