The Design Review process helps with other challenges of an engineering team like:
Inter-org communication. Often people don’t know what other folks are working on. With very large teams you might even have two different engineers working on the same problem and not realize it.
Surfacing legacy work. Due to having design reviews, engineers can know that a particular technology problem had already been solved in the past.
Onboarding new engineers. Always a challenge due to legacy systems but design docs and reviews create easily digestible documentation.
Productive contribution. Design Reviews make it easy for a whole range of engineers to contribute thoughts towards a design. Often times little details are caught because someone with a different point of view jumps in. It also helps make it easier for shier engineers get involved due to the Questions Doc (detailed below)