I am also not convinced that a "crypto winter" decreases the difficulty accordingly (in percents).
Correct.
While bitcoin price has decreased from 63,800 dollar to 37,500 (about 41%), the difficulty has decreased only about 14%.
Even when the price dropped to 3,200 dollar from 19,800 (about 83% decrease) in December 2017 - December 2018, the difficulty increased nearly 200%.
The difficulty has been increasing smoothly all the time.

Source:
blockchain.com