Well now, there you go, showing off how clear thinking you are.
I hadn't looked at it that way, just instinctively thought. So I checked. Colombians need a visa to transit Canada. So your thinking works. So all I am left with is that at BOG they do not have to but they have promised to allow me to transit without fee. Which I can if all on one tix, not if separate tix (if no interlining).
(Also checked if Colombians have to go to Bogota for the biometrics. They do not! ... they could alternatively go to Medallin LOL)