Windows 2016 standard support 4 vm's in Hyper-V
that's not correct: Also with Server 2012 R2, there were only 2 Windows Standard Server VMs included in the license. So there is no downgrade to W2K16 Standard.
See here for Virtualization Rights on Server 2012 R2: https://hyperv.veeam.com/blog/virtualization-rights-windows-server-2012-r2/
Tim Cerling commented
Anthony - not sure what you mean here. Windows Server 2016 Standard, even 2012 and 2008, are able to run more than two VMs on a system. The number of VMs that can be run is limited by the hardware on the system. There is nothing in Hyper-V that limits you to 2 VMs on any of these operating systems.
That said, there is a licensing limitation. Windows Server Standard (2008, 2012, 2016) grant the right for the simultaneous execution of two Windows Server Standard VMs, but it does not enforce any technical limitation to the number of VMs that can be run simultaneously. It does not even enforce the legal limitation of two Windows Server VMs.
Where are you seeing this restriction?
This is degraded from server 2012 R2 standard where i am able to run more then 2 vm's on a system at a time. If you aren't going to have a product between standard and datacenter then don't hamstring us with wanting to use 2016.