Scheduling collisions possible in IaC - Infrastructure as Code - solutions vs. software defined data center?
I disagree with your definition, kubernetes, openshift and other are scheduler and as such should go in the SDDC part. IaC things are Vagrant/Terraform/Cloudformation/Vmware Cloud management. They are about writing code to define the infrastructure.

With this in mind k8s may fit both, a deployment.yml is IaC to drive the k8s SDDC.

Let take exemple for a k8s cluster running on top of vSphere infrastructure:
You have a scheduler k8s on top of another scheduler vSphere. SDDC on top of another SDDC.  

K8s is concerned by its node load (which are vSphere VM), vSphere is concerned by its nodes load (ESXi hosts).
With this in mind k8s will move pods (containers) around its nodes, where vSphere will move k8s nodes around its hosts.

This indeed could lead to a spike or freeze of k8s nodes when both wish to move their loads at the same time. The solution is just an architecture solution: disable vSphere DRS on your k8s nodes so there won't be a move of your k8s nodes around while they are already moving containers.

Each time you overlay systems with the same behavior, you have to plan their definition properly to avoid race conditions. 

Worst case would be running a docker swarm cluster on top of kubernetes on top of mesos on top of vSphere infrastructure on top of Nutanix partitions. (Absolutely doable but I don't think anyone would do that out of demonstration purposes)

So yes, this setup makes sense, it mainly require a careful design of all layers to achieve the best performances.