About the thread I linked: I think that, at the time, the firmware selector was still in the works and wasn't the go-to method for finding firmware for your device. As such, people used one of two main entries into the downloads - a link from the main page at downloads.openwrt.org that leads directly into the into the specific version's subdirectory, or the 'releases' directory with all versions... this is where people would find the newest (and officially not yet released in these situations) version in the directory. So, my recommendation at the time was to always use the main page to navigate to the newest officially released version, rather than digging through the entire listing of releases.
Now, to be clear, the firmware selector is a huge improvement over the previous method of browsing those directories. I don't know exactly how the firmware selector builds its list, but I suspect it just searches the downloads directories and updates accordingly. I had actually put in a feature request at the beginning of the year that would allow new versions to be suppressed from display until someone flips a bit during the release announcement process. I don't know if this would be easy or hard to implement, but I agree that this could cause some confusion for some users. The good news is that it is a temporary situation -- usually just a matter of a few days and everything should be good. Hopefully that FR will find its way to implementation at some point, but coding is not my forte so I can't be the one to help bring it to life.