Steve, containers don't virtualize data, but as you correctly note SQL Server containers without data offer limited utility. You imply that SQL Server containers aren't supported with database cloning. This isn't accurate.
Windocks is a SQL Server container solution (all editions of SQL Server 2008 onward), that includes database cloning using the same APIs as Red Gate SQL Clone. Windocks supports use of clones with all SQL Server instances (Microsoft containers, both Linux and Windows, and conventional instances). We see growing interest in containers as light-weight instances, when combined with SQL Server cloning is an awesome environment for dev/test, and reporting/BI. Many customers also want to use clones with conventional instances, including developers workstations and servers. Just wanted to ensure that readers have the complete picture!