I often get accused of over thinking things. and I can live with that

Thing is, like i said, I have spent a lot of time trying to understand the performance of wire and cable. Mostly coaxial cable for extremely fast pulses with risetimes measured in billionths of second. So when I see things like slid vs stranded, I HAVE to figure it out. Based on what I found in the wire tables there is no mystery. It is just due to differences in copper cross-sectional area. In a given gauge, solid and stranded don't have exactly the same copper area so they don't have the exact same resistance.