It's important to note is agreement being everyone can live with the decision. I.e. it's not really a bike shedding thing. Just that nobody has strong objections (the reason being is that if there are strong objections there are probably good reasons for that and ideally those are understood before taking the decision).

At the end of the day, if there was a time critical decision and there was no consensus someone like a project manager would make the call. I haven't actually seen that happen, a well functioning team/project generally is able to make decisions.