Anyway, although we're talking about ordering of RMDs and QCDs, here is a link to a BH post where they talk about the ordering of RMDs and Roth conversions, which is a similar but distinct topic:
https://www.bogleheads.org/forum/viewtopic.php?p=7222461#p7222461
It's possible that the link there points to some stuff which might shed light on the ordering of RMDs and QCDs. I haven't looked.
I took a closer look, and there is a link in the above link that appears to point to the CFR where the poster thinks this ordering rule comes from - question 7 in particular.
I've read that question, and I'm not convinced it says what people purport it to say.
What it seems to me to be saying is that if you have a $60K RMD, and you do a $55K ordinary distribution and a $10K Roth conversion during the year, then the first $5K of the $10K Roth conversion is not eligible for conversion. There are consequences to that, of course.
But if you make a $30K ordinary distribution, then a $10K Roth conversion, then another $30K ordinary distribution, then the Roth conversion is totally fine, even if it happened before the full distribution was made.
In other words, the conflict only arises if you don't meet your RMD in full during a given year. I think the first dollar rule is to give the IRS a regulation to enforce what happens in that scenario if a Roth conversion also happened - they don't want to have to take ordering of transactions during the year into account. And this makes sense because the IRS doesn't get all of the transactions during the year; they just get the year end totals. With the first dollar rule, they can enforce things with just those totals.
It all turns on whether you think:
"the amounts distributed during that calendar year are treated as required minimum distributions under section 401(a)(9), to the extent that the total required minimum distribution under section 401(a)(9) for the calendar year has not been satisfied"
Does "has not been satisfied" mean at the time of the distribution, or at the close of the taxable year? The language is not dispositive in my opinion.