I don't think we have ever seen such a reversal, the closest might be Microsoft's attitude towards open source, but that is apples and oranges.
Facebook used to be more open. You could connect to Facebook Messenger using any Jabber/XMPP. They never reversed course, if anything they made it harder to use Messenger without the application.
The next Reddit CEO will turn up and their grand plan will be to invert whether or not the company loves/hates developers using their API.
Then they'll try to convince developers to come back, because "this time I've really changed".