If you have clean network path from your terminal to the dev vm, why need for either ProxyCommand or ForwardAgent - just ssh to the vm directly, no?

Of course local, not forwarded ssh-agent on the terminal would be super-handy to avoid typing pass-phrase time and again; but that's different and independent from ForwardAgent.

I do ssh directly to the VM. It sits behind a VPN connection at aws. I need to make ssh connections from there to github. The key resides on a smartcard in my laptops usb slot. And that's where ssh-agent/ForwardAgent comes into play. I forward my local key to the remote VM.

Fair enough. Makes perfect sense, thanks!