Often also, the basic structure already exists from previous factory use, so that can speed it up also.
Ok let's just pretend there are enough previous factories read to accumulate nearly a million mining gear.
Each difficulty period, the difficulty cannot change by more than a factor of 4. This means the difficulty cannot increase by more than 400%, nor drop by more than 25% from one difficulty period to the next. This means that if it took five weeks to find 2016 blocks, the difficulty would only drop by 25%.
I have a strong feeling you are wrong, based on this code which enforces the difficulty limit
if (nActualTimespan < nTargetTimespan/4) nActualTimespan = nTargetTimespan/4; if (nActualTimespan > nTargetTimespan*4) nActualTimespan = nTargetTimespan*4;
It means the difficulty adjustment can be anything equals or greater then 75%.
So for simplicity, a 10T difficulty can change to any number between 2.5 and 40, unless i am reading code wrong which is unlikely but i got old anyway.