Remington actions not being sold separately, it is very common for a complete rifle to be purchased, disassembled for the action, and the parts sold to offset the cost.
If a person is building up a custom rifle with premium barrel, this makes sense. But I don't know that it is reasonable to automatically assume that a factory barrel is junk. I suppose it all depends on what the expectations are.
A friend has a rifle made up on a .308 700P, still with the factory barrel. Restocked, HS magazine system, Holland muzzle brake. It shoots really well, and is competitive in sniper competition. Would it be inherently more accurate with a custom barrel? Maybe. But the rifle can win matches as is. Once the factory barrel is shot out, it would be time for a custom. Might be just as competitive.