Nice. Really wish it would apply to Lambda too. Or that Lambda have another kind of reserved capacity plan (similar to DynamoDB perhaps).
I don't think it's likely happening for Lambda anytime soon. I can neither confirm, nor deny that I know anything about the underlying costs for Lambda.
Source: Ex-AWS employee.
Yep looks like about 20-50% based on commit.
That's correct. The same commit allows you to run workloads across EC2 and Fargate (note that the discounting is different).