A safely home canned food depends on the entire canning process from heat-up, through processing time, and finally cool down.
The cool down process should not be delayed once the processing is complete, and in the case of pressure canners, the depressurizing step. Leaving jars inside a closed canner slows the cooling process greatly. If thermophilic bacteria are present, they can survive and grow. This leads to flat sour spoilage, an undesirable sour flavor and smell, and compromised safety of the food.
Allow the pressure to drop on its own, remove the lid, wait five minutes and remove the jars to cool at room temperature.
Source: https://extension.psu.edu/is-my-sealed-jar-safe
After water bath processing, turn off the burner, remove the canner lid, wait five minutes and then remove the jars to cool at room temperature.
