Hi Danilo,
Thanks a lot for this report.
We're going to fix the bug. It should be in Instant Terra v1.10 to be released next week.
BTW if you only have 2 possible values, it may be better to use a On/off parameter node: it's displayed as a check box.
You can also use a List parameter node. It's displayed as a combo box.
In Instant Terra v1.11 to be released in April this year, you'll also have the possibility to display it as a list of radio buttons or a list of images.
That will be available for components, custom Python nodes and custom GPU nodes.