It does in the rare instance that you have coded checkboxes with underscores.  There was a bug in the API that deleted the underscore from the coding in the variable name.  For instance, if you coded your checkbox

a_1, Red,
a_2, Blue

The variable names come out of the API as 'color___a1' and 'color___a2'.  

This bug was fixed in Version 5.9.1, but since the API doesn't have a way to return what version of REDCap is in use, this will make sure the proper names are in use for earlier versions.