where it says available on fdroid it links to their personal fdroid repository. plenty of projects both open source and not have their own fdroid repository. fdroid is both a repository that only allows open source software and a packaging infrastructure tool for people hosting their own repositories. based on the fact their claim that they are on fdroid literally hyperlinks to their fdroid repository i don't see how anyone could find that misleading. if anything it's fdroids fault for giving their own repository the same name as their infrastructure tool instead of doing what every other project did and give them separate names. for example docker and dockerhub, flatpak and flathub, etc.
here is a list of 100+ not official fdroid repositories.
https://github.com/userkilled/FDroid-List-Repository