Why does a field appear twice as an option for conditional visibility?

This results from a change made to allow integrations to pull in just  id or just the label of checkboxes and dropdowns. Although a field will appear twice - you'll see that one version of the field shows - label and one shows - id after the field name. 

When you are selecting a field for conditional visibility, either option may be used, but the - ID may be preferred as it usually won't change. In a lot of cases it's hard to know what the id will be - especially if it's coming from a form typeahead or user typeahead.

The - Label can change in certain circumstances depending on the type of dropdown selection, but is sometimes what you need to use for the conditional visibility rule. 

For example, imagine the following setup:

Dataset A - Document A:

• has a title of "Biology Informatics"

Dataset B - Document B:

• has a selected value of "Dataset A - Document A" in a field. The label is "Biology Informatics". This field is set to auto update when the linked document is updated
• has another field that shows when the lookup field's - Label is set to "Biology Informatics"

Now someone updates the field linked to the title in Dataset A - Document A to read "Bioinformatics". That updates the label in Dataset B - Document B for the lookup field, and now the conditional visibility rule will hide the other field and delete whatever data was in there.