Is there a loss of taste when pressure cooking bitter gourd?
Taking into consideration your purpose for eating bitter gourd, and your objective of cooking it quickly, to “lessen the cooking time”.

The fastest way to cook it is to stir fry it, with eggs, meat or just by itself with some oil, garlic and shallots. from prep to eat time is about 20 minutes. Or add it to a chicken broth for a quick blanch before consuming it as part of a soup.

From experience, pressure cooking it will not save any time, rendering the bitter gourd into something lumpy and not as palatable.  Part of the older generations belief is that it also loses its “medicinal” and nutritional benefits.