I'm confused... used the firmware selector to get a version of 23.05.5 for my Rpi4. Seems to build just fine, downloaded a file with 23.05.5 in the name. I didn't get any errors when flashing it, but OpenWrt still says 23.05.4 on the status page.
Very strange... the system does act like a new image has been installed. Just for giggles I tried the factory image and flashed a new SD card, and that says 23.05.4 too!