Usually, pocket holsters are recommended for pocket carry. Breaks up the outline of the gun, orients the grip properly, protects the weapon and secures the trigger area.
If you use a pocket holster, the trigger guard is covered (on a well designed holster for revolver or semi auto).
So, even though it's in your pocket, if it it's in a holster, you have to clear the holster before firing. The advantage lies in having your hand on your weapon discretely at any sign of trouble.
So, shooting through the pocket is not feasible if a holster is used.
If shooting through a pocket, a revolver with an enclosed (or at least shrouded hammer) is needed. You will have to shoot purely by feel...and with one hand...and, perhaps, multiple times, and you may still need to draw and deliver follow up shots, perhaps with a reload, after the initial round(s) are fired through the pocket.
That's something that should be practiced, first dry, then, and VERY CAREFULLY, live, on the range (if you have access to a range or safe place to shoot that will allow it!)
Overall, I'd say the benefits of holstered pocket carry outweigh the benefit of being able to shoot through a pocket when carrying WITHOUT a holster.
I would rather spend my training time practicing a smooth draw from the pocket and then practice delivery of rapid, accurate shots...practicing both close contact, below eye level shooting, with one or two hands, as well as eye level sighted fire with one or two hands.
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