So did they test every dying person on influenza, and if they died, cause of death was "influenza"? What if they tested positive for both influenza and Covid-19

So did they test every dying person on influenza, and if they died, cause of death was "influenza"? What if they tested positive for both influenza and Covid-19, what cause would be listed? I'm just not convinced the comparison is very meaningful, as I suspect many more people were tested for Covid-19 than for influenza. The testing strategy may have been completely different, making the comparison meaningless.