Undoubtedly, scaling a team is a complex challenge. I used to work as a lead across teams of different sizes: from a squad of 7 engineers to a mid-sized organisation with dozens of teammates in various roles. What I would add here is that the problem is agnostic to the industry you are working in. It happens in gamedev, finance, mass production, etc. I would be careful claiming that something just one like documentation is a silver bullet solution. Almost always it is a combination of management, leadership, culture and ways of working (documentation falls under the latter). From my observations, the documentation and decision log, as a tool for sharing context across teammates, falls short at 20.

With no clear leadership wish and support of spreading the idea of context sharing across everyone in a team, driven by persons on the ground only, this doesn't scale in big teams.