Just a note to say that by using a few extra tools (the security implications I still need to understand, caveat emptor etc.), I was able to get the SSH integration working fantasically well in Windows Subsystem for Linux (WSL).
The tools use a couple of programs to expose named pipes as unix sockets in WSL, which the ssh-agent can then use to authenticate.
I used the steps outlined here https://stuartleeks.com/posts/wsl-ssh-key-forward-to-windows/ and added the script to my .bashrc file (don't paste random scripts from the Internet without knowing what they do, check this is right for you before using it, etc. etc. :))
Hope it helps someone somewhere... :)
1Password Version: 80600027
Extension Version: n/a
OS Version: Windows 11 22543.1000