"The way it's written implies that gravity is in some way unreliable..."
Well, in a sense it is. Though certainly Airbus is perfectly able to design gear that lock down if "manually" extended, a less well-designed airplane can have gear that free-falls but, because of excess airspeed, fails to engage the downlocks. If that happens--it's a consideration on certain GA aircraft--you don't have hydraulics or electric jackscrews to push the gear into the downlocks once you've slowed adequately. And no, they sometimes won't simply click into place as you slow, because the downlocks require something of a thump--free fall under gravity--to engage.
You're being too hard on the journalist.