No this is false. You can rest a twenty pound weight on your collar bone, lift a similar weight, etc without breaking it obviously.
It is true the collar bone is relatively fragile. The reasons for why this might be are a matter of some debate. Biomechanics studies (orthopedists love biomech studies) suggest that over 1500N are required in axial load. Tension, shear, and twisting forces will decrease this in an unpredictable way (the clavicle has a fairly irregular shape) but it’s far more than 7 lbs.
[The clavicular fracture: a biomechanical study of the mechanism of clavicular fracture and modes of the fracture. Harnroongroj T1, Tantikul C, Keatkor S.]