Points are final! 100K in the MR account.
So here's what I did (and I don't profess to say that I was anything more than lucky).
3BM (mb plat, reg amex plat, and Blue Cash Preferred). All got approved without needing to call in (took a few hours for some though). First amex plats for me.
Added MB plat to an existing Amex account and created new account for reg amex plat. Noticed MR#s were the same though.
Next, I hit both spending limits on the same day.
Then I waited. Got antsy after still seeing nothing in the Amex account page and SMed them about moving up my statement date. While learning that any change in statement date would actually push the closing date to the following month, I also learned that they could see both my accounts with that one SM. I also learned that I had 100K points pending in my MR account.
Now the points have arrived in my Amex account page and finalized in MR. I'm not sure when they arrived...as my closing dates haven't arrived yet, so perhaps it's just a 7-10 business day wait (spend threshold met around the turn of the month)
Good luck to anyone else who tries it!