I have found that if a new dev build gets posted while Rockbox Utility is already open/running and connected to the internet, the "Development Version" listed in the "Rockbox version to install" menu doesn't get updated though the version that gets installed will be the new one and not the one listed in the menu. The listing still does not change after the installation is completed. I looked for a way to manually get that menu to update itself but I think the only way to do so is to relaunch the program. This was with the 1.5.1 version for Windows released on 2022-04-18.
I have also noticed with the Mac version 1.5.0, if I have a two volume ipod6g mounted within Rockbox Utility and then click the Eject button I get a notification that says "Device successfully ejected - You may now disconnect the player from the PC". But in fact only the volume containing the installation of Rockbox was ejected - the other volume remains mounted on the Finder's desktop - so if I unplug the iPod, the Mac tells me "Disk Not Properly Ejected - Eject [my named iPod] before disconnecting or turning it off." This happens with both Bootloader USB Mode and Rockbox USB Mode. I realize that having a two volume ipod6g is kind of a hack so I don't necessarily expect Rockbox to fully support it, but I thought it was worth mentioning. (The Apple firmware doesn't support a two volume ipod6g at all, of course.)