What practical control is completely lost once a pressure cooker is sealed and pressurized mid-cycle?

Ability to taste, add seasoning, or introduce herbs.

A significant drawback of sealed pressure cooking is the absolute forfeiture of real-time process control. In traditional stovetop cooking or oven use, a cook can periodically lift the lid, taste the developing sauce, adjust seasoning by adding salt or acid, or introduce fresh aromatics or herbs mid-way through to build layers of flavor. Once the pressure cooker is sealed and the internal pressure builds up, safety mechanisms prevent the lid from being opened. This forces the cook to rely entirely on initial measurements and pre-planning; any mistake in seasoning or realization that a flavor element is missing must wait until the entire cooking cycle is finished and the pressure has fully dissipated, eliminating the crucial opportunity for immediate, adaptive correction.