If the professor indeed claimed authorship of the test before giving it to the students, why shouldn't they use that test bank to study? If the professor didn't

If the professor indeed claimed authorship of the test before giving it to the students, why shouldn't they use that test bank to study? If the professor didn't write it, the test bank is just similar questions which should be excellent practice for the test. If he didn't this is just further lying from cheaters, but that sounds exactly like something many a professor would claim casually in a class. If he did say he wrote the test, then all of this is a professor playing cover his ass after telling students he's writing a test when really he was just test bank spelunking.