I find the colony debate strange. The Sector, as a whole, is on the decline so multiple 10^7 colonies or more popping up randomly makes little sense.
I couldn't care less what the arbitrary cap is to colonies as long as colonies operate, mechanically, the same. I think it odd that there is an expectation for a colony to grow from 1,000 to over 10 million or more in the span of 10-15 years. Soft caps or no, I know I won't be playing 30 in-game years just to see a colony go from 10^7 to 10^8, especially considering there is no in-game benefit for doing so. There's no realism to be achieved here so an arbitrary value doesn't bother me in the least.
I don't understand the fixation, honestly. It's an immersion thing, sure, but there are way bigger fish to fry.