Hi jason,
the script is good. In the help of the Update-Tools -NoReboot parameter is says:
Indicates that you do not want to reboot the system after updating VMware Tools. This parameter is supported only for Windows operating systems. NoReboot passes the following set of options to the VMware Tools installer on the guest OS:
/s /v"/qn REBOOT=ReallySuppress"
However, the virtual machine might still reboot after updating VMware Tools, depending on the currently installed VMware Tools version, the VMware Tools version to which you want to upgrade, and the vCenter Center/ESX versions.
It looks like you had a version of the VMware Tools that needed a reboot. 