The problem with no collaboration is that it can lead to fragility. Context transfer is costly, but without it work bottlenecks around key individuals. When those individuals are explicitly disincentivized to transfer knowledge preemptively, you lose the slack in the system. Vacations and exits become more fraught. Deadlines are harder to hit reliably. You have less systemic resiliency.

Instead, encourage targeted collaboration (in particular, pairing: collaboration with a goal of accomplishing something) within the scope of a team, and avoid cross-team collaboration, which is the expensive part.