Currently lifeform XP works like this to my understanding:
Pick your planets lifeform (Example Mecha) - Run discovery missions - Finds Mecha XP - Mecha levels to 10 (bonus giving 1% to LF techs on that planet) - Bonus is giving based on Mecha level to all chosen research irrelevant of whether that research came from another lifeform (example Human).
My suggestion is to make it so each lifeform research is effected only by their corresponding lifeform XP level.
For example, Human technology (Intergalactic Envoys) Would be affected by Human XP level.
Mecha technology (Plasma drive) Would be affected by Mecha XP level.
Reasoning, to me this is how I thought it worked just by intuition until I found out it did not.
It would also make sense that finding human XP on discoveries would have the purpose of adding bonus to a human technology, giving purpose to finding all lifeforms irrelevant of the planets chosen lifeform.
Since most people will end up choosing the same lifeform on all planets depending on play style but picking technology from a range of lifeforms I think this makes sense.
This would be a QoL update in my eyes and seems logical(?)