I seemingly found another way water gets into the trunk. I concluded that the water runs down the channel around the top of the trunk toward the rear and then must run past or over the taillight. That is where it seeps past the gasket between the light and the metal body of the tail-end of the car. I figured this because the water left dirt deposits below the taillight as a sign of it’s path.
Good deduction. I’ve seen this several times myself including a cracked tail light lens. I always replace the gasket but I use clear silicone sealer on both sides.