Fair enough. For clarity:

The proof of work threshold for a block (aka the difficulty) was the same when the fork started. The function that adjusts the difficulty (a function of time-between-blocks) is the same across both forks. It would take considerable time for the non-fork chain's difficulty to adjust to where it can make blocks at pace with the fork chain again. And even if it did, the fork would represent less work due to a lower difficulty.