> You pay for the amount of vCPU and memory resources consumed by your containerized applications.
How does vCPU fit into serverless architecture?
> Pricing is based on requested vCPU and memory resources for the Task.
Tasks being a collection of Containers. This is simply a container service like ECS or EKS.
> Pricing is calculated based on the vCPU and memory resources used from the time you start to download your container image (docker pull) until the Amazon ECS Task terminates.
This means you pay for the resources that were started for your containers until the container ends. Including all idle time and any overprovisioning you did because you have to tell it which instance type you want. Compare that to the pricing of Lambda where you only pay for the time your functions need to execute when they get called based on external events.
To bring this back to the beginning of the discussion: Complaining about docker because it is not a good tool for serverless architectures is not smart because it is not used in serverless architecture offerings. Fargate uses containers but it is not a serverless service. Fargate is a container service that tries to simplify setup of compute clusters in comparison to ECS, EKS and EC2.