Those who uninstalled should try to delete the "smartdb_Volume(b731de 13-d6f2-4b75-99b****.sdb" file Bitdefender left in the "Syetem Volume Information" of each partition.
Yeah, it's present in each partition
@Minimalist made me aware of it in another thread.
Even Kaspersky leaves a file named "klBackupDepository.dat" in the "System Volume Information". Kaspersky left this file in both partition of my SSD, but wasn't present in the HDD partition. TBH, I'm disappointed at both's uninstall process due to this. They shouldn't write files into locations they can't remove.
As per user Minimalist's suggestion, I booted up my Macrium boot USB and used CMD to delete them.