They can simply force all users to file bugs with technical details OR get a support contract for general questions and troubleshooting, which would be the best way of forcing companies into contracts.
They changed how a feature works and they communicated it via changelog I don't know what they should have done more. They have no service contract with ms.
I love how you just continue the lie. I linked to the changelog. Feel free to quote from there where "they communicated it via changelog". That's not even getting into how it's a shitty argument anyway, especially with as shitty of a changelog as ffmpeg has.