That study is complete horse shit. Self reporting is notoriously unreliable, particularly when setting aside ego and some level of introspection is involved. Criminals lie. WTF would you expect them to tell the truth about how often they practice. Also, you count cranking off a few rounds on a dope counter as "practice"? Come on.
Take a look at self-reporting of what guns criminals carry. Then take a look at actual records of what was confiscated. They don't match. Lots of "Glocks" are Hi points. Even "back in the day" they *say* they carried a .357 Python but got caught with a .25 Raven.