I apologise for my post not being clearer, I was busy with handling another matter IRL just now and just posted that semi-quickly and thus may have been less clear than I liked.
I meant that from the results I have, it's clear that for the Saltmarsh Chits drop rate is tied to the named item drop rate. However, thankfully they (Chits dropping) do not impact on named items dropping themselves (from the results I have looked at here, one dropping does not impact on the other appearing or not). This (chits drop rate being related to named item drop rate) is not the same (at least from what I remember) to other similar systems; such as the Ferrocrystals - which as you have noted appear to have more parity with the Hay from Saltmarsh.
The test results were all done via Back to Basics end Chest only on Normal (Heroic), as they were the quickest one to drag another toon in to test if the Elixirs of Discovery bonus is working correctly; by using a bunch of toons without the elixir, and identical built toons with an elixir. Tests show that Normal does indeed drop at 10% and that with the Saltmarsh Elixir (15%), the drop rate is indeed being applied additively to reach ~25% drop rate.
Anyone wondering about a "normal" elixir, I will be continuing those tests later too. But thus far, I have no reason to believe they are not working as described.
J1NG