I’m not exactly sure what you’re referring to, I answer too many questions here to keep track 😛
Anyway, the value of the field you’re checking has nothing to do with the value of the other field unless you make it.
What exactly are you trying to do? Are you trying to validate one field based on another field? If this is the case then what you want to do is use an acf/validate_value filter https://www.advancedcustomfields.com/resources/acf-validate_value/
You can look at other values or other fields by looking at $_POST['acf']['KEY OF OTHER FIELD']
