I believe the color cameras after the TK-41 also sent RGB to the CCU (Camera Control Unit) as you surmise, but really, if the chroma encoding circuit design had to be changed from NTSC to PAL, what difference did it make where it was located?
By the way, the TK-41 used separate coaxial cables for baseband R,G,B. Later cameras used triax:
https://en.wikipedia.org/wiki/Triaxial_cable
I believe this still carried R,G,B signals, but frequency-multiplexed on RF carriers so they could be sent via a single conductor.