why cant I have small plants in big pots
Simply put, roots dont like to wander on there own for too long.
This can lead to stunted growth, slowdown in plants metabolism and can stress the plant.
Stages are best: especially with clones that dont come with an inbuilt security feature. i.e.the taproot.
Am big on testing the status quo, but for plants sake, use incrementally larger pots (i go root it sponge, 1 or 2L pot, then final, all still allows roots to maintain strength and vigour.
I also use mycos on roots which i see as a shot of adrenaline, when transplanting, mycos only good on root contact.
There is a huge archive online about root dynamis and the like, worth a few hours research.
Good luck.