Registration from within PluginTracker does not create a new user. (it has a field called "registration", which then shows the registration fields in the tracker form)
The same process from the registration script does work (user created, and item in user tracker created also).
Reproduced in the show instance:
Add a new item through the Plugin Tracker, and the new user is not created, just the tracker item:
Add a new user (and tracker item) through the registration form, and the user and tracker item are created successfully:
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