Why did Alloy Analyzer stop supporting the exh and part keywords?

Questions
1 
/**
 * Generate an error message saying the given keyword is no longer supported.
 */
static ErrorSyntax hint(Pos pos, String name) {
    String msg = "The name \"" + name + "\" cannot be found.";
    if ("exh".equals(name) || "exhaustive".equals(name) || "part".equals(name) || "partition".equals(name))
        msg = msg + " If you are migrating from Alloy 3, please see Help->QuickGuide on how to translate models that use the \"" + name + "\" keyword.";
    return new ErrorSyntax(pos, msg);
}

The grammar used by the parser still holds rules to handle the keywords, but it chooses to call CompModule.hint to output an error message and CompModule.hint has a check specifically to warn about migrating from Alloy 3.

I don’t need to use these keywords. I am asking this question merely due to my own curiosity. Thank you!