Why Did This Coffee Jar Propagator Not Need Venting?

These fuchsia shoot tip cuttings have been sealed in a 200g inverted coffee jar since 23rd October last year, over 10 weeks ago. They are just starting to show signs of growth, so should be about to take root. Since the propagator has been on a window sill kept at low temperatures (5 to 10 deg C (40 to 50 deg F)), I thought it wise to have a look inside.

Removal of lid produced a sharp intake (or outtake, I'm not sure which) of air, indicating the seal had been better than expected. The cuttings seemed disease-free apart from the dead flower buds infected with a fungus, presumably 'Botrytis' (one bud has been removed and placed on compost surface). With temperatures having run closer to 5 deg C for most of the time, I am surprised to see so little damage.

I don't understand how these cuttings could be sealed up completely, whereas dahlia cuttings taken last summer and covered with a freezer bag had to be vented by cutting a hole in the bag to prevent rotting. Presumably it has something to do with the temperature, though not sure what. It is certainly not humidity; condensation has been on the cooler side (the one nearest the window) of the jar since day one.