I’m going to respectfully disagree in regards to motor oil, but I do agree with your point about the tranny service.
Regardless, if a fluid level is low, it needs to be topped off. I’m just curious if an added benefit would being able to extend the OCI due to the introduction of new fluids.
In the case of my Corolla, we will find out, because at the rate that it uses oil, it’s going to of had several quarts added before I change it.