The ruling does not say this. The RR clearly avoided asking the question or ruling on the answer.
If you reversed the situation and sold at a loss in the IRA ---
Wait! A sale within the IRA is not "a sale at a loss." It is ignored for tax purposes.
So reversing the situation, deliberately ignored by the author, technically does not occur.
Moreover, I consider myself a very small fish in this ocean.
If I even thought of challenging the RR, I would consider myself required to file a Form 8275 or 8275-R, which is the "Hey, IRS, I'm disagreeing with your dumb RR, and if you don't like it, you go ahead and disallow my client's return and I;ll see you in court."
Speaking just for me, i) I am not that type of person, ii) I have no standing to represent clients in tax court, and iii) I like my clients.
Finally the RR does make sense to me, and I can't say I disagree with it.