Taxonomy treated as category or tag


I'm playing around with custom posts and I found something very particular.

In Studiopress's Agentpress child theme, when you create a taxonomy (and create some values for it) and you create a custom post, you select values for the taxonomy the same way than for a category (with checkboxes).

But with CustomPress plugin, when I'm going to select values for the taxonomy created, the interface is the tag's way (that is, a text box where you can enter random values).

This is a screenshot:

What can I do to change the behavior and make it work the "category way"?

Thanks in advance.