I've done plenty of runs using D'art equipped with 2nd lvl Snatch from Gran as an extra ability (Especially for the Advent battles).

What I noticed generally is that while the number of chests increases noticeably on any characters that you killed with Snatch on them, the number of gold (not sure about platinum) chests significantly decreases.

This was most noticed back when I was doing the Apocalypse and Phoenix events where using snatch on mobs as well as the boss allowed me to obtain 2 pages worth of drops, even though the frequency of dropping gold chests noticeably decrease as well.
Anything above the Snatch level of 5 on the enemy started decreasing my gold drop rates all the way down from 0 to 1, while if I don't use Snatch, I would consistently get around 1-2 per run.

This raises the question, how does this "Item drop rate" increase works?
Does it simply increase the drop rate of the bronze and silver chests thus causing the drop rates of gold to significantly decrease?
Or is it something else? If so, is it even worth using Snatch at all in these new buffed up drop rate Advents?