You’re incorrect.
Data > Make changes to a thing > select some thing with a Boolean field > field to change “the boolean field in question” > value “Checkbox Whatever’s is checked” (alternatively this last part can be “Checkbox Whatever’s isn’t checked”)
“is/isn’t checked” is the Checkbox’s equivalent of the “value” field.
“is checked” returns yes if the checkbox is checked / no if the check is not checked
“isn’t checked” returns yes if the checkbox is not checked / no if the check IS checked
(So, in essence, the Checkbox input has a boolean not operator built in.)
More exciting info on Booleans, checkboxes and related matters: