Parameter confusion on car dev

I still somehow find it strange to have staffs at my level but not regarded as a 5 star. There are also occasions from transfers to even my own HQ having staffs one higher than my level but instead those are regarded as 5 star. I don't even know what parameters are measured to determine their qualities.

In advance this even goes to the research power. I used to know the research power is determined of star level aggregation between CD and TD. Which mathematically everyone understands, but someone told me whether 4.5 power or 5 star power aren't any different. And within my observation, i guess that is fact as shown below...

5 star CD & TD