While it is true that dac_override is granted by the log-observe interface, that meant for dealing with log files who have different ownership than a root-running process (as many logs tend to have different owners).
Sometimes a dac_override denial pops because ownership is not properly setup by the snap (if you are using the system-usernames, you might see "Ownership (discretionary access controls) in System usernames (though you might find it helpful for understanding how dac_override is enforced)). Is your snap using system-usernames?
What are the ownership and permissions of the files that snap.soscleaner.soscleaner is accessing when you see the denial? Perhaps there is something you can do in your snap or something we need to adjust in a different interface.