Checked the official fandom page, under rod enchantments, for Treasurer it says,
+0.5 Item Chance Multiplier
(increases the chance of items (including Sunken items)
being caught, doesn’t affect fish)
But b4 ppl said that item chance doesn’t increase sunken rates, soooo is smth like a treasurer bronze rod or a treasurer collectors rod better to get sunken?
A while back, a tester/vetex staff member (i forget) said that item chance on fishing rods does not affect sunken chances. Since nobody could disprove this, we all assumed it was true.
However, recently vetex has said that item chance does affect sunken chances. Not everyone has heard about this, so some people still believe that item chance is useless.
However, due to how sunken pity works (it seems to ignore item chance), an Ensnaring Bronze Rod is still probably the best option, since catching (roughly) 50% more fish is just as valuable as each fish being 50% more likely to be a sunken, high catch rates means you get more sunkens from pity, and catching 50% more fish also has the useful side effect of getting you 50% more fish scales.