OKI MC563 scanimage with --source "ADF Duplex" saves only the first side/ page

I noticed since i got my OKI MC563 scanner that when I scan images using the duplex scan mode available for this device, only the first image is saved.
I thought this is a bug of Skanlite, but I could also reproduce it with Simple Scan and now I tested it using the scanimage CLI.

When executing this command:

scanimage -v -v -v -d escl:https://192.168.1.30:443 --resolution 200 -x 210.000 -y 296.985 --mode Color --format=jpeg --batch="sid-600-%03d.jpeg" --source "ADF Duplex" > out.txt 2> err.txt

... the scanner or ADF unit indeed looks like it would do a duplex scan of all pages in the tray/ feeder (?), as it draws all pages through and uses the duplex mechanism.

However, there is only one file generated in the process : sid-600-001.jpeg Here is what the stderr looks like:

scanimage: value for --resolution is: 200 
scanimage: rounded value of resolution from 200 to 200
scanimage: value for --x is: 210 
scanimage: value for --y is: 296.985 
scanimage: rounded value of br-x from 210 to 210
scanimage: rounded value of br-y from 296.985 to 296.985
Scanning infinity pages, incrementing by 1, numbering from 1
Scanning page 1
scanimage: scanning image of size 1653x2338 pixels at 24 bits/pixel
scanimage: acquiring RGB frame
scanimage: min/max graylevel value = 6/255
scanimage: read 11594142 bytes in total
Scanned page 1. (scanner status = 5)
Scanning page 2
scanimage: sane_start: Document feeder out of documents
Batch terminated, 1 page scanned
Closing device
Calling sane_exit
scanimage: finished

No output occured on the stdout. I am on Manjaro Unstable (so basically Arch Linux packages).

scanimage --version                                                   INT ✘ 
scanimage (sane-backends) 1.3.1; backend version 1.3.1