The about window gets the version number from the package.json file, which in this case still says "version": "0.11.2" for the newest update. An oversight on their part, but not something that is impacting you in any way.
You can either ignore it, or report it on their GitHub.
According to my pacman output my package version is same as yours (0.11.4-1.1). But when I open Readest and then check the version inside the app it shows 0.11.2 instead.
Could you open readest and then check the readest version in “About Readest”
I know basically nothing about AppImages, but I assume based on what you said that it includes the latest commits after the update was released, which includes the update to the package.json file I mentioned earlier.
It looks like the commit you mentioned wasn’t included in the 0.11.4 branch, as it seems to be missing the version update commit. Hopefully, release 0.11.4-1.1 includes everything except that specific version number change.