That's not exactly how the FAA interprets it.
By definition, a model aircraft must be “flown within visual line of sight of the person operating the aircraft.” P.L. 112-95, section 336(c)(2).1 Based on the plain language of the statute, the FAA interprets this requirement to mean that: (1) the aircraft must be visible at all times to the operator; (2) that the operator must use his or her own natural vision (which includes vision corrected by standard eyeglasses or contact lenses) to observe the aircraft; and (3) people other than the operator may not be used in lieu of the operator for maintaining visual line of sight. Under the criteria above, visual line of sight would mean that the operator has an unobstructed view of the model aircraft. To ensure that the operator has the best view of the aircraft, the statutory requirement would preclude the use of vision-enhancing devices, such as binoculars, night vision goggles, powered vision magnifying devices, and goggles designed to provide a “first-person view” from the model.2 Such devices would limit the operator’s field of view thereby reducing his or her ability to see-and-avoid other aircraft in the area. Additionally, some of these devices could dramatically increase the distance at which an operator could see the aircraft, rendering the statutory visual-line-of-sight requirements meaningless. Finally, based on the plain language of the statute, which says that aircraft must be “flown within the visual line of sight of the person operating the aircraft,” an operator could not rely on another person to satisfy the visual line of sight requirement. See id. (emphasis added). While the statute would not preclude using an observer to augment the safety of the operation, the operator must be able to view the aircraft at all times.
1 For purposes of the visual line of sight requirement, “operator” means the person manipulating the model aircraft’s controls.
2 The FAA is aware that at least one community-based organization permits “first person view” (FPV) operations during which the hobbyist controls the aircraft while wearing goggles that display images transmitted from a camera mounted in the front of the model aircraft. While the intent of FPV is to provide a simulation of what a pilot would see from the flight deck of a manned aircraft, the goggles may obstruct an operator’s vision, thereby preventing the operator from keeping the model aircraft within his or her visual line of sight at all times.
(https://www.faa.gov/uas/media/model_aircraft_spec_rule.pdf)
What this seems to prohibit is the use of goggles that obstruct the observer's vision. It does NOT seem to prohibit looking at the FPV on a tablet/phone as long as you can still see the aircraft.
What seems clear - and, indeed, I don't know how so many on this forum don't seem to get it (or maybe care about it) is that YOU MUST BE ABLE TO SEE YOUR AIRCRAFT AT ALL TIMES WITH THE NAKED EYE. ("
the aircraft must be visible at all times to the operator", "the operator must use his or her own natural vision (which includes vision corrected by standard eyeglasses or contact lenses) to observe the aircraft"). This precludes these multi-mile missions that some people are apparently flying all the time where they cannot see their Phantom - or any potential hazards that it might encounter, stationary or not.