"A virtual CPU is whatever Amazon wants to offer in an instance series."
No. The vCPU (Virtual CPU) aspect of an AWS EC2 Instance is the county of virtual cores that are exposed to an OS. In desktop computers, a quad core Intel CPU will appear to have four courses when looked at from inside the OS (my go-to way to count them in Linux is to run top and press 1). A quad core hyperthreaded Intel CPU will appear to have 8 cores. The vCPU metric simply tells you what the OS will show you, and tells you how many processor threads can run concurrently.
"If you deal with server sizing and instance price comparison, then the measure -- previously expressed as an EC2 Compute Unit or ECU -- is kaput."
Yes, ECU (Elastic Compute Unit) metrics are still used behind the scenes, but Amazon does publish them. Even for new Instances. Check out these URL's:
Of course, this isn't very parsable by human eyes. So someone started an open source project to display this data, and its available at http://www.ec2instances.info/
So yeah, TFA is wrong.