Last month, it was discovered that Samsung was sourcing the storage cleaner feature on its devices from a shady Chinese company Qihoo 360 which is known for stealing user data. This created quite a stir in the Android community which eventually led the Korean company to issue a clarification stating it only sends generic data to Qihoo's servers and that the entire process of scanning and removing junk files from devices is managed by it.
It looks like to be on the safe side, Samsung has completely removed the storage cleaner feature from the Device Care app in its devices. The company has released an update for the Device Care app updating it for Android 10 which also does away with the storage cleaner feature, though the change-log does not mention anything.
An APK analysis by a Redditor also confirms that the library sourced from Qihoo 360 has been removed from the app, though some strings related to the cleaner feature do remain. Nonetheless, if you were uncomfortable with Samsung sourcing a feature from a shady Chinese company in your device, you can now rest easy. It is possible that the company will bring back the feature eventually after building it in-house or sourcing it to another company.
You can find the Device Care app update in the Google Play Store. If the update does not show up, you can grab the latest APK from APKMirror and sideload it.