Definitely not your method holding them back. I usually use moist paper towels too (all white - no dyes), and I used to put them in plastic containers exactly like you do. But now I put the moist paper towels in a ziplock bag, and place that in a Priority Express Mail envelope (about 9x12), and I hang that up in a warm place. The envelope keeps the beans in the dark, and hanging it up ensures the taproot heads straight down, which makes them easier to transplant.