Yes, it’s in the math.
for the rest of this example, I’ll use a 20 player raid, everybody’s unsaved.
The way PL worked, is that is that it picked 4 player to get loot, then randomly chose an item to give them.
Let’s make the numbers easy, and say that this boss drops a ring, and 3 other items for each loot spec, and for comp I’ll use Echo’s WF Razageth comp (1 or 2 of every class) assuming everyone’s loot spec is for the one they are playing.
In order for the bow to drop for the 1 hunter, the game needs to decide 1st that the 1 hunter gets loot, then the 1/4 roll for which item has to roll the bow, giving the bow an expected drop rate of 1/80 (1/4*1/20), or 1.25%.
For a caster staff to drop, 8 people can loot it. This puts the expected drop rate at 8/80 = 1/10, or 10%.
For the ring to drop, the 1st roll doesn’t matter. Everybody can loot and equip every ring. And since no matter who the 1st 1/20 roll decides gets loot, the odds of seeing the ring are just about 20/80=1/4, or 25%.
The fact that PL chooses the person 1st guarantees that some items will drop a lot more than others, as their drop rate is directly proportional to how many people in the raid can use it.