Perhaps because they're not advocating for letting 1/8th of a congregation in, but all of the congregation.
previous to the complete lockdown MD where I live was restricting congregation size, so a middle road is possible
To stop you and your family from being exposed to the virus.
And potentially my family, if you decide to cough on my groceries after the service. since you think it's safe to shop, congregate in large groups, etc.
very few things in life are entirely safe, e.g. many more people die from traffic accidents than will die from covid-19