Hub and Spoke - New tunnels being added to configuration.

Whilst working on some VPNs, I noticed something odd, I have my FortiGate acting as a Hub for some branch sites, using BGP over the tunnels. I added a new site to site VPN for some other traffic and I noticed it got added as a spoke on the Hub and Spoke config? I deleted it from there but it then deleted the BGP config as well! its nothing to do with the hub and spoke set up, so why is the site to site VPN peer going in there?