What are the odds for a Pokemon to have its secondary type vs. its primary as the Tera Type?

Question

If you catch a Pokemon like Toedscool, what are the odds it will have a grass or ground type tera? Same with breeding.

I was thinking maybe the Tera types of the Pokemon themselves could affect the odds when breeding, because when I first began breeding a "perfect" Toedscool (IVs/nature), I found that only 2/16 Toedscool had grass tera typing, which is the secondary typing on Toedscool. I did:

1. Electric tera Amoonguss with normal tera Toedscruel. All six eggs were ground tera.
2. Normal tera Toedscruel with ground tera Toedscool. Eight eggs were ground, two were grass.
3. Ground tera Toedscool with grass tera Toedscool. 13 eggs were ground, 17 eggs were grass.
4. Ground tera Toedscool with ground tera Toedscool. Five eggs were ground, five eggs were grass.

Maybe it's all just 50/50 and I my first batch of guys were just outliers, but according to this SSS, I think there may be a way to skew the odds. I ran these "tests" because it was what it took to get the IVs I was looking for along with the grass tera. If you don't have the bona fide answer or you're not labbing this out, maybe just leave a comment of your findings, if anyone still IV breeds these days >_>

Comments

btw of the 56 eggs I got no shinies >:(

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They are both 50/50. However, a Pokemon with a special tera type, ( The glowing gold ones) will be 100% of a certain type that isn't STAB.
Source: https://www.keengamer.com/articles/guides/how-to-change-your-pokemons-tera-type-in-pokemon-scarlet-and-violet

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About my answer, breeding was not taken into account, so it may have been something to do with that. Sorry abt no shinies btw.

Answer 1

Normal wild Pokémon found in Paldea typically have a Tera Type that matches one of their normal types. This Tera Type does not reflect their potential evolutions and cannot be passed down through breeding.

Source

Furthermore, while reviewing spawn data while playing, I can confirm that neither of the types are weighted. The tera type is chosen when a Pokémon spawns in the world, and the only thing that affects the choice is radiant rng (that is to say all the factors that the game uses to create "rolls" such as steps taken, button inputs and other actions taken).