They are canvassers. Their role is purely non-discretionary.
Their only job is to add the votes from the counties, and agree that they added the numbers correctly, nothing more. It's just math — their step doesn't include any kind of "are these votes valid or not" decision making.
Even if there were a recount scheduled, this step is required to get the total, since no body prior to this has the right to add the votes from two counties together.
They literally just add the votes from each county together to create the total numbers for the state.
If one or two of them refuse to add the votes together, or to certify the votes were added together for each county, then a court will order them to do it.
This "refusing to add the votes" has happened before in Michigan. The last time involved some sort of abortion related addendum to some county's ballot. And a judge ordered them to do their fucking job, and they did it. Here's an article from the Detroit Free Press about it
if you want to learn more about how odd this situation is.