--complex-tca in Lensfun, how does it compare to the normal tca correction?

When creating a CA profile in Lensfun I can choose
$ lens_calibrate --complex-tca tca

or just

$ lens_calibrate tca

Why would I want to choose $ lens_calibrate tca

And what target would work for tca correction? Parking place/garage windows, yes. But what about a white sky and branches of a tree like this one Olympus 25mm 1.8 - is this amount of chromatic aberration normal?: Micro Four Thirds Talk Forum: Digital Photography Review