The claim was, "If you tell Alexa, 'buy me a chromecast", it orders you an Amazon fire stick instead.'" None of the articles you linked describe that happening

The claim was, "If you tell Alexa, 'buy me a chromecast", it orders you an Amazon fire stick instead.'" None of the articles you linked describe that happening. It seems pretty unlikely. Perhaps at one point it suggested a Fire Stick as an alternative, but it doesn't seem to be doing that currently.