Heist Chests have x% chance to contain more valuable uniques potentially not working

Has anyone experienced "more valuable uniques" from heist chests (assuming under the definition of legion/metamorph where "valuable unique" means league specific) at all because I don't believe this mod is working. I've tried with both heist chests and the reward chests (ones behind rogue doors) and I've not had a single league specific unique drop from them. Either that or the chance is super low but I would of expected across 150ish+ heists that a league specific unique would of dropped from one of the heist chests with a 10% chance.

Or is "more valuable" operating under the Harvest definition where uniques are ranked via their perandus coin cost?