Adam,
I hope all is well. Yes and No.
Let me clarify for you. The Add-VMNetworkAdapterAcl cmdlet is used to create an ACL to apply to the traffic through a virtual machine network adapter. When a virtual network adapter is created there is no ACL on it. Given a list of IP-based ACL entries to be applied to traffic in the same direction, the longest match rule decides which one of the entries is most appropriate to apply to a specific packet.
The Add-VMNetworkAdapterExtendedAcl cmdlet is used to create an extended access control list (ACL) for a virtual network adapter. The ACL allows or denies access to a virtual machine network adapter for network packets based on source IP address, destination IP address, protocol, source port, and destination port.
Both do slightly different things, but are both focused on the Virtual Adapter targeted. This may or may not result in the restriction of access to/from a VM per se, as it would depend on the number of virtual adapters available in the VM and whether or not an ACL or Extended ACL had been applied to all.
Cheers !!
Adam