What I don't understand about their response is: why not make it configurable? Admittedly this is my philosophy for almost every product I work on - "make it maximally configurable, but make the defaults maximally sane" – but I'm baffled every time I hear someone talking about this 'dilemma'.

You just keep your simple interface, but allow the power users to, say, click through to a particular menu and change their setting – the setting in this case being ~"let me provide feedback / configure how recommendations work". For that kind of user, finding a 'cheat code' is actually a gratifying product experience anyway.