I have to admit if the time scale was as you say then I don't know if I would have looked at the DG either! I also would have made a quick descent straight ahead with the caveat that if I didn't get VMC again when I thought I would be then its an immediate climb to MSA.
As for the actions of your RHS pilot, you mentioned about him not having flown much, flying simulators and starting IFR training. It makes me wonder if he was looking outside at all and maybe was just looking at the 6 pack/screen in front of him! I know that doesn't match what he said but I am sure we all have bent the truth or tried to excuse our errors at some point in the past when caught out. At least if this IS what he did, you had more chance of him not turning off heading!