This is a quick post as I saw this problem this morning on a computer running Windows 10 TH2 release [Version 10.0.10586]. When checking for the new Virtual TPM feature it wasn’t present on my Hyper-V Gen 2 VM but it was present on a colleagues TH2 install, both of us were at the same version of Windows 10.
Verify if the computer was installed with a clean install of Windows 10 or upgraded from a previous Windows 10 build.
If it had Hyper-V installed previously and was then upgraded (like mine from Windows 10 build 10240 to 10586) simply uninstall the Hyper-V feature and then reboot when prompted, then reinstall it along with installing the Isolated User Mode feature which is required for this functionality.
The un-installation of the Hyper-V features will not uninstall or remove any of your vm’s which will appear back in Hyper-V manager after the feature is reinstalled.