My opinion is that the Line Shoe might be best for someone that has a mountain biking first bent to their riding, and if they ride back roads, well then these shoes would be a comfortable, durable choice, with the caveat that they might be a bit toasty on hot days and that their wide stance may interfere a bit with certain bikes/riding styles.
As long as it isn’t too hot, these are actually pretty nice shoes for pedaling out on the gravel. My thought is that these would be better choices for warm to cool weather climates. Hot, humid areas will require shoes with more venting than the Line shoes have. Wide feet? These could be your shoes then.
The Line model from Giant is actually a development in conjunction with the Giant racing team and aimed at enduro mountain bikers. These types of shoes typically have more foot protection and a nod to walk-ability and with that, traction off the bike. Giant felt as though these might also be traits a gravel road rider might be interested in.