21 minutes ago, StephenEsven said:The rules do not say that a ship overlaps an object when it is placed underneath it.
A contradiction would be if the rules say a ship does not overlap an object placed underneath it, and having an official ruling say that it does overlap. One says yes, the other says no. In this case, the rules say nothing, and the ruling says it overlaps. One says yes, the other says nothing. That is a clarification, not a contradiction.
QuoteAnd the rules for devices explicitly states that it must be placed underneath more than one ship to detonate immediately.
There is no rule stating that a device must be placed underneath multiple ships to detonate immediately; the rule you are referring to only tells us what happens when multiple ships overlap, not that multiple ships are required. The FAQ/official rulings thread tell us that whenever an object is placed underneath a ship, that ship overlaps it. That is enough to cause proximity mines/ion nets to immediately detonate when placed beneath a single ship.
It's important to remember, by the way, that the RRG is not the only official rules source for X-wing. It's the most important one, absolutely, and when there is a contradiction between the RRG and another rules source the RRG wins. Unfortunately, however, the RRG is neither comprehensive nor perfectly drafted. If you're not willing to accept FFG's official rulings as official then there really isn't much discussion to be had, because you're simply not playing with the same set of rules as everyone else.