Can anyone throw some inputs what it exactly is?
I believe it is a strategy, similar to core-satelite approach that mitigates misfit risk in the alpha generating portfolio.
The completeness fund is combined with your alpha generating portfolio to form an overall portfoilio that tracks a specific index of the general market. This way, your alphas are kept, and your tracking error decreases.
I believe it requires more frequent rebalancing because active risk profiles of active managers can change frequently
it is just a sub-portfolio that is added to align your active portfolio with the benchmark, so your portfolio + completeness portfolio = benchmark (with same risk factors)