narvik

It appears different locations have their detectors set at different sensitivities.
In China -for instance- a watch, belt buckle, and/or metal framed sunglasses might trigger the "red beep". The same items will not sound in the USA.
Although they are allowed, I also take watches and belts off in order to hopefully prevent a secondary screening/pat-down.

Added:
I see OP seems to be talking specifically about the new scanners. The scanner will definitely "see" the watch, necklace, and point to its location on the crude body image on the monitor.
It would be up to the security personnel to determine if that is worthy of secondary screening or verification. To improve the chance of "clear passage" I still recommend to take those items off.