I've seen more people who posted they got an extra chest, and had some myself as well. I'm hoping it's a minor update to the quest, since especially the 80-stamina map desperately needed the improvement. Wasting 80 stamina on 4 lvl 5 manyus, which happened pretty frequently, was kind of ridiculous. Thanks to this update (which I hope is intentional), an SG is still good, since all the chests are guaranteed gold, giving a fair chance to get lvl 100 manyus out of them, but no longer the only efficient way to farm manyus.