As developers we had 2 months, in which we had to do beta testing also. Then there’s the edge issues which won’t appear until the app is released to a wider audience, then there’s Apple’s “Bug Fixes” which introduce new bugs or include undocumented changes which break apps that were working.
Journalists are often completely unaware of the difficulties encountered by developers with beta releases. Some of them have never, ever, touched code.
FCP in Sierra is definitely broken - I got confirmation from my 3rd party Plugin Developer about my issues described here. He confirms that he had to change his installation routine AND that Apple brought in some bugs in media encoding/decoding… as developer he could manage to fix this though we both wait for Apple now