Security applications normally (usually) have the option to scan the whole device, be it a cellular device or pc. The scanner checks files, notes, messaging, browsing, etc. I don’t see this as an option within Bitdefender Mobile Security.
The answer is straightforward. If Bitdefender Mobile Security includes a full scan option that scans Android system files, it wouldn't make sense because even if Bitdefender finds any malware in Android system files, it won't be able to remove it. This is because the Android OS has control over the applications running on it, and it doesn't allow any antimalware application to remove system files. Therefore, Bitdefender only scans for third-party installed applications in .apk format on the Android OS.
Talking about the other antimalware vendors that check files, notes, messaging, it is still not of any use since the malware that can attack the Android OS has to be in .apk format.
Regarding browsing, Bitdefender for Android offers web browsing protection that scans for malicious/phishing websites in real-time, allowing it to block any websites containing threats
The other antimalware vendors that provide a full scan in their antimalware applications are of no use. They tend to consume more Android memory, causing the device to slow down in functionality due to the real-time protection enabled.
OMEN Laptop 15-en1037AX (Bitdefender Total Security) & Samsung Galaxy S22 Ultra (Bitdefender Mobile Security)
A very insightful post from @Flexx above.
To add here, Mobile Security will make sure that the Android device stays clean by automatically scanning any application immediately after its install. So, it will no longer scan those apps that have been scanned before or that have not been altered in any way. The only scanning option on Android is to scan the storage or not, and this is enabled by default. You can adjust the Scan Storage option from the Settings menu. However, it won't scan system applications, because applications installed in those locations cannot be uninstalled anyway and should not be infected in the first place.