At times, the nec not only seems ambiguous, but sometimes hypocritical. They will list open air well lights with par 36 bulbs that have exposed connections and carry bulbs that can be up to 75 watts (an exposed 75 watt bulb alone covered by some really dry leaves comes across as risky to me). I have done repairs on well lights after heavy rains where the connections are still wet from sitting in water and not being able to drain fast enough to avoid potting the water. The Nec also has a bunch of rules that bounce between temporary and permanent connections.
You can drape 120 volt christmas lights over trees on the inside and out, hang them from your gutters, etc, etc as long as it's only a "temporary" application. What is temporary, 1 day or 3 months?
As for the 12 gauge wire requirements, that's new to me, but doesn't surprise me. Kind of goes against the practice of 25 foot leads that many manus use, but im not sure what the rules are. From what I have seen on the NEC requirements, permanent low voltage lighting systems require 6 inch depth, plus 18 inch depth under hardscapes. I have seen a few commercial jobs that are close to this practice, but probably 1 out of 50 residential jobs that are. Im not saying that this makes it ok, im just saying.