From what I understand, it’s not so much that all disagreement is to be avoided entirely, but rather that it should be done on an individual level prior to the meeting. So the fundamental difference is that a western company may use the meeting as an opportunity to discuss and debate an issue, whereas that process is done before the meeting in Japanese corporate culture.
Yeah, the concept of "nemawashi" (根回し) is very important there, this idea that all the groundwork and decision making is agreed upon before the meeting happens.
The term literally comes from the concept of "preparing the roots", that is, the process of softening the ground and trimming around the roots of a tree (often a bonsai) in preparation for moving it safely.