They do. It might be people who had COVID and got the vaccine and died. It might be a guy who falls off a ladder, but they might not have his medical chart or medical info, so they have to mark it down as a fatality. These are all possibilities.
Its done like this because 1) They don't want to ignore something and then get sued and 2) It errs on the side of caution and is frankly good practice, because its better you have all of the data then let something slip by.
EDIT:
Also, remember, the Pfizer study I'm talking about is being done to find out what adverse effects there are, not their frequency. So in this case, they will try to document everything under the sun.