@Run&Gun You‘re right.
From the R5 manual:
Set the recording method for movies.
Records movies to the card selected in [ Record/play].
• Auto switch card
Same as [Standard], but recording ends when the card becomes full. When you resume recording, the camera switches to the other card for recording. A new folder is created after switching cards.
• Card 1 RAW, Card 2 mp4
For each recording, a RAW movie is recorded to card 1 and an MP4 movie to card 2, both with the same file number. When one card becomes full, recording is no longer possible.
A user on another forum that I'm on that has the R5 reported that there is dual card recording in 8K RAW modes.
8K/30P RAW + 4K DCI IPB
8K/24P RAW + 4K DCI IPB
8K/24.00P RAW + 4K DCI IPB
I interpret this to mean 8K RAW is recorded onto the CFexpress card and 4K onto the SD card.