i planted a couple of seeds from a colombian purple brickweed years ago .. to my sorprise it was ready from seed to bud in arround 70 days .. crazy
What I've heard is the cultivators in Colombia- and other "landrace" locals such as Jamaica- started crossing their long flowering sativas with shorter flowering indica strains which could be why you see the 70 days, and assuming it's real Colombian genetics you found. Researching strains I've found seeds marketed as true Colombian that suggested the Colombian genetics may have been crossed at some point with a shorter flowering strain.
It stands to reason growers might have bred the true 18 week flowering out of their crops, but still a dream of mine to eventually find some true landrace Colombian beans.