Enhanced Tracking Protection is using the Disconnect domain list. ipinfo.io is listed in services-relay.json and mdl-services-relay.info, which I believe makes the Disconnect.me product route requests to these domains through their proxies to prevent IP fingerprinting.

Should be noted that IPInfo doesn't get blocked with tracking protection set to "standard". Users have to set tracking protection to "strict" to run into this issue. When they do this, they get warned that this setting may break sites.

I don't think Mozilla/Disconnect will make an exception because privacy-infringement is a potential risk with a service like yours if used by malicious websites. I wouldn't put too much effort into this, the people affected by this are a fraction of a fraction of the general web audience and they've already seen a warning that websites may break because of their choice.