Isn't the difference based on time though? The device manufacturer can push a patch, but they would get access to the information after the patch, whereas access to the log gives you information from before the patch. Or have I misunderstood?
However, if important data is retained in logs, then the manufacturer could grab the data from the logs. They can get information from a time before they decided to look into you.
It's like a wiretap vs access to a diary. A wiretap only gives you information after the tap has been installed, whereas getting your hands on someone's diary would give you access to previous information too.