Pressing to the dark fabric is not a 'written in stone' rule. Before trimming the HST's, I would only lightly finger press the seams and then lay out the block so that I could see which way the seams need to be pressed to make them nest. Then press and trim the HST's and put it together.
I had a pattern with the same problem and the writer did not indicate which way to press the pieces. Since I had to make 20 of the problem blocks, I always kept one on the ironing board for reference.