Most of the "proof" comes from reading the applicable regs and seeing what they do say rather than what we think they might say. Just 2 examples from this thread:
91.109(c) does not say:
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Except when in Class B airspace, No person may operate a civil aircraft in simulated instrument flight unless -
(1) The other control seat is occupied by a safety pilot who possesses at least a private pilot certificate with category and class ratings appropriate to the aircraft being flown.
(2) The safety pilot has adequate vision forward and to each side of the aircraft, or a competent observer in the aircraft adequately supplements the vision of the safety pilot; and
(3) Except in the case of lighter-than-air aircraft, that aircraft is equipped with fully functioning dual controls. However, simulated instrument flight may be conducted in a single engine-airplane, equipped with a single, functioning, throwover control wheel, in place of fixed, dual controls of the elevator and ailerons, when -
(i) The safety pilot has determined that the flight can be conducted safely; and
(ii) The person manipulating the controls has at least a private pilot certificate with appropriate category and class ratings.
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and 91. 113(b) does not say:
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General. When weather conditions permit, regardless of whether an operation is conducted under instrument flight rules or visual flight rules, and except when in Class B airspace, vigilance shall be maintained by each person operating an aircraft so as to see and avoid other aircraft. When a rule of this section gives another aircraft the right-of-way, the pilot shall give way to that aircraft and may not pass over, under, or ahead of it unless well clear.
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