Hello TAH,
Yes, it is very simple, and very, very, fast. You don't even have to think about it. You just reach for the knife handle, and your hand action of grabbing it, opens and releases the knife.
I imagine the guy that designed this sheath, knew exactly what he wanted.
After several days of researching, I spoke with Dick Murray, from Murray Custom Leather Company. He told me this sheath was made by, and hand stitched by, his younder brother Jim Murray, who had his own business in the late 60's into the 90's, but passed away in Dec. 2003, and Jim's company is no longer in business. He said Jim was in the marines for 4 years, and was likely very proude to make this special sheath for a serviceman.
Dick said the snap release is definitely his dad's design. (George Murray)