re: How do conference-only games prevent the spread of coronavirus?

Because conf games only allows flexibility
You are most likely going to have to cancel or postpone SEC games if a team has several positive tests
So let's say Fla Tenn can't be played in Sept due to positive tests on one team than you could have schedule flexibility to move it to a later date for the weekends that will be set aside if you have to do that.
With an eight or ten game schedule that will free up weekends to shift the schedule as it will be a moving target for everyone
Now if the cancellations start to pile up than at that point you pull the plug on the season