I have hardware running AMT 3.2.1. I am using SCCM SP1. I believe I'm only using 'inbound' provisioning, since all of my vPro hardware are also SCCM clients.
Is it true that I will not require a separate provisioning certificate, since SCCM can leverage the security of the SCCM client?
You will still need a separate provisioning certificate, commonly referred to as the "remote config certificate" to provision your systems. The SCCM client only initiates the provisioning process. The remote config certificate is still used to secure the actual provisioning process itself.