I don't understand the fascination with MacUpdater... I tried it... and it reported multiple apps with updates, but three of them (Firefox, Dropbox and AppZapper) were already up-to-date.
I'd say it's unreliable at best...
Hmm, I've never had that happen, and have been using MacUpdater for over a year and have Firefox and Dropbox. Sometimes apps get updated, but not pushed to the built-in-app updater, so if you check for updates it says up to date, but if you go to the website there's a new version. Also sometimes apps get updated but the version number doesn't change (different build number though).
The developer is super responsive, so if that happened to you send him an email and he'll check the specifics for that case, and fix it quick. App is in active development. I'm amazed by the dev, it's a 1-man operation, he handles the coding and the customer support, and sends me long and detailed replies always to any doubts I have.
Fascination is because there's nothing else like it (MacUpdateDesktop sucks in comparison and is a resource hog (and more expensive, and doesn't find as many apps/updates as MacUpdater)) and some people are update addicts (personally I manually refresh my iOS app store updates several times a day lol). MacUpdate finds updates for non-MacAppStore apps that don't have a built-in update mechanism very well, also finds updates to extensions and software that aren't really "apps".
And another reason: sometimes it's easier to update an app via MacUpdater than via the apps built-in system! Onyx and other apps that direct you to a .dmg download for example. MacUpdate handles it much better: downloads, mounts, replaces, unmounts, deletes, much faster.