A Dual Boot does need activation. And each copy of Windows is supposed to have it's own license. But, using the same version (not necessarily the same Build), will usually activate, because the activation is tied to the device. You will probably find some people using Insider Dev, Beta, and Public all on the same device (multi-boot) and all activated, with only one license. Using a VM is creating a new (different) device, hence another license for activation is required.