Lambda actions at an aggregate level are not supported.
The reason the platform is unable to act on Lambda functions on Aggregate level policies is due to the fact that an ARN would not be able to be assigned to that function. In a per-resource level policy, the platform can specify the ARN of the asset the function needs act on. In an aggregate policy, there may be a collection of assets and CloudHealth cannot provide ARNs for all of them which is why this functionality is not supported.