Your change actually slightly nerfs reprocessing asteroids, since in the base game you get on average 1/3 of each of the other two types per chunk consumed, but with your nerf it becomes about 0.28 of each. If you changed the amounts to a 10% chance of getting the same asteroid back and a 30% chance of each of the other types, then the ratio is restored and you get reprocessing back to base game effectiveness while having the same nerf on quality casinos. This change does make reprocessing slightly faster, but you could make the recipe slightly slower to compensate (which would nerf asteroids even more).

Feel free to take this idea or leave it, but your changes seem interesting and I might give this mod a try once I finish with my current run.

Is it possible that you have some other mod installed?
The vanilla chance to get a different asteroid type is 20% each, 40% stays the same type, 20% loss.
With Rebalance it's still 20% each, 30% same type, 30% loss.
Wheres the 1/3 chance or 0.28 coming from?

i agree, the ratios do seem changed unintentionally. The question is : when I am reprocessing 1 asteroid type specifically in order to generate the other types, how many e.g. metallics do i need to get 100 carbonic and 100 oxide? In vanilla, if i start with 500 metallic, then i will get 200 metallic back with my 100 carbonic and 100 oxide, so the net expenditure is 300 metallic -> 100 carbonic + 100 oxide.

For your mod currently - if i start with 500 metallic then i will get back 150 metallic with 100 carbonic/oxide, so the expenditure is 350 metallic -> 100 carbonic + 100 oxide.

Under the proposed change, it would be, start with 500 metallic then get back 50 metallic and 150 carbonic 150 oxide, so the net expenditure is 450 metallic -> 150 carbonic + 150 oxide, the same ratio as vanilla, and 50% faster as OP mentioned.