Resource guarding is a fear based behaviour and it can often be treated, but it can also be a genetic, inherited tendency that is managed rather than cured.
You may be able to find them on here if you search for them but I know I have definitely seen on here threads demonstrating the type of 'inherited severe resource guarding' I am referring to in golden retrievers.
Puppies of just 9 or 10 weeks biting viciously enough to draw blood, guarding ridiculous items like blades of grass.
Spaniels also are known for it, and as a pp mentioned, cockerpoos are rapidly getting a reputation as guarders, from the spaniel side.
Personally, I have never ever understood the 'leave alone when sleeping/eating etc' mantra.
I think it is dangerous.
I think it is extremely important the dog understands that it can be moved by you or have food or toys taken at any time without getting aggressive.
I don't agree with aversive resource guarding prevention training by removing bowls, I think that makes aggression more likely but I definitely think dogs must be taught that people around precious resources = good things.
Some people don't seem to mind dogs that growl a little when disturbed or over food and things but it would be a deal breaker for me.