Constraint is the action of prevention, not the principle to which we appeal to justify the constraint. Sure, you can use subjective criteria, but then one can also be a loofa face shit gibbon.
Doesn't make it true or right to use a subjective opinion.
For example, a squeeze job can go in within 4 feet of an existing line, if the protection is all clean and not fixed. Then the objective experience of the climb isn't modified by the FA author.
A bolt placed within an arms reach of another bolt is prima facie understood to be squeeze, unless the holds dictate a movement that prevents the climber from being able to reach the other holds on the other climbs, unless they can be linked via moves of the same or lesser difficulty.
Doesn't mean that someone wouldn't create an intersection of a climb to another climb, breaking that principle, so we would need an exception to the principle for routes that intersect or another principle that says the intersecting route shouldn't bolt next to the bolt on the first line; perhaps in a way that would mislead a climber on the first line.