Is this influenced by this legacy seed vs. "new" seed that I saw on the Advanced Options?
Here let me go into a bit of an explanation. There are basically 3 ways rng will function for a majority of things in the lastest versions.
1. Using 1.5 (and before, though there have been minor changes in even older versions) rng: This includes step-related weather, dish of the day, item drop placements for geodes not advancing daily, a sort of flawed travelling cart selection rng, clay/winter forage moving in predictable patterns, etc.
2. Using 1.6 rng: This makes a few more things seeded (like mainland rain now being seeded), fixes the old cart rng to be more even, added more machines to the tile/seed/time system of drops instead of them relying on game1.random (like a few did previously such as bait makers and slime presses iirc), makes clay tile advancing patternless, etc.
3. Using 1.6 'legacy' RNG: This is sort of a mock 1.5 RNG, it is important to note that it
is not exactly 1.5 RNG, it is like a puppet show of 1.5 rng, with clay farming that's very very slightly different, weather back to being step-influenced. Notably, not all rng changes are reverted, the cart is still the 'fixed' 1.6 version (which is why no cc speedrunners really run it over 1.5 in legitimate attempts), those machines using game1.random I believe still use the 1.6 tile/time/day overlay.
So, to answer your question, kind of? If you select the legacy rng you'll go back to a step-related weather system, and it should be the same as 1.5, but with 1.6 you instead have a seeded system that is disproportionately sunny due to some restrictions placed on what days become rainy (I don't want to spout anything untrue that I can't remember perfectly right now so I'll do some research or check some of my old messages to get info on them).
