I wonder if it matters which night you do the points stay and which night you do the cash stay...

Hilton's system usually only allows for one "rate code" on a given folio.

I had this happen once before but I had made two reservations. I actually did check in and then check out and then check back in (did not change rooms). My first night was Points and Cash, the other was MVP Rate. I still received two night credits and one stay credit. I received the proper number of points for the full cash night rate portion (as well as restaurant charges and parking charges made) and nothing for the Points and Cash one (as expected).

Oddly when I tried to pull the bill online, Hilton had merged the two reservations into one "stay" (as expected) and the folio came up showing nothing but the total charged to my card (nothing itemized) and the rate type, etc. column was blank.