yes cold slows down development.
there's a concept in agriculture I think is usefull to envision it, 'degree days'.
I think an autoflower is pretty comparable to crops like wheat which also don't have a daylength-trigger to start flower.
you can distinguish different phases in development, can be pretty simple like germination, emergence, veg and flower, but it can be much more detailed(like each node/new leaf appearance as phase).
development rate is how fast the plant progresses to the next phase, independent from growth rate(which is just gain in overal biomass, so for example a plant can get larger leaves if growth rate increases or development rate decreases, smaller leaves when just development rate increases without increase in growth rate, etc).
and development rate has a temp optimum, and a base temperature below which no development occurs, and a range between it(there's also a similar range above optimum temp, with again a limit when it stops).
so a usefull way to standardise it over different years/locations, is using the unit 'degree day'. let's say you need 100 degreedays for the next phase, with a base temp of 10 degrees celsius. then both 10 days of 20 degrees or 20 days at 15 degrees add up to 100 degreedays.
and if you know the needed degree days for a full grow from seed to harvest, you can calculate when you can expect to harvest based on weather data.
so in your case, you don't want to hit base temperature(but can't tell you what that is, it varies between species, development phase and between strains), but as long as you're enough above it that development doesn't slow down too much, I think it could be positive.
because while development rate slows down at lower temps, growth rate is less affected, so you could be getting a bigger harvest since you can get more growth before it's ripe.
although there might be some weedspecific negatives to low temps, my observations tend to be that the later plants that get lower temps in flower get more leafy buds. but not sure wether coincidence/genetic variability, or actually an effect of the low temps.
