There is a retaining cap for the freehub body that's threaded onto the axle. It definitely does not come off with just a tug. You definitely do have to unscrew something to get the freehub body to come off. You evidentially unscrewed something. The manual for the powertap has a good cut-away illustration of how the hub is put together.
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Cat 2 Track, Cat 3 Road.
"If you’re new enough [to racing] that you would ask such question, then i would hazard a guess that if you just made up a workout that sounded hard to do, and did it, you’d probably get faster." --
the tiniest sprinter