>>"Developer relations" normally implies a role intended to encourage developers to use your platform.
no, thats marketing.
Dev relations works with you once you are already using the platform. Don't get their intentions confused. They may be on your side with bug fixes and feature requests, but if you try to do something that goes against their company, why the hell would they be on your side?
It's a facet of marketing, sure - but you're marketing your platform/API/library/company to developers, not the general public. It doesn't really matter whether they're currently using your system, since they might be in the near future.
The implication is that by having a large ecosystem with lots of developers, the company will benefit, but in this case, FB appears to have shot themselves in the foot.
All the liaising in the world is not going to help you when all the developers who use your platform think that you're an asshole, or you're too busy managing your ad portfolio to pay attention to them.