Interesting idea. Yet another thing to try in the brewing hobby.
My inclination would be along the lines of added work for no extra
benefit. The way to find out would be to brew a couple of identical
batches using traditional techniques on one and the pressure cooker for
the other. But you have to boil the wort anyway, and if the hop flavor
gets extracted by boiling, then using a pressure cooker is just an
additional step that adds nothing to the end product and does not save
any time.
On the other hand, if the flavor extracted using the pressure cooker is
somehow different, or lasts longer, or has better aroma, or adds some
other significant improvement to the end product, it might justify the
extra hassle. Just as it wouldn't save any time, it wouldn't add any
either.