Detached ruleset scopes affected — Recording an error reporting

When I refer to the code in the manual for testing, I found the detached ruleset scopes affected.
( use webstorm and less 2.6.1)
View code,Please visit Less manual

Reads as follows

Variable and mixins accessible form definition win over those available in the caller:

@variable: global;
@detached-ruleset: {
    // will use global variable, because it is accessible
    // from detached-ruleset definition
    variable: @variable; 
};
selector {
    @detached-ruleset();
    @variable: value; // variable defined in caller - will be ignored
}

compiles into:

selector {
    variable: global;
}

If you add additional code in front of manual reference code,for example:

//additional code
@testvalue: 2px;
#test {
    width: @testvalue;
}

//manual reference code
@variable: global;
@detached-ruleset: {
    // will use global variable, because it is accessible
    // from detached-ruleset definition
    variable: @variable; 
};
selector {
    @detached-ruleset();
    @variable: value; // variable defined in caller - will be ignored
}

compiles into:

#test {
    width: 2px;
}
selector {
    variable: value;
}

The value of variable: global becomes value;
At present, I can not explain why.
I can only record as an error reporting.

Start with the detached-ruleset scoping example in the Less manual and reproduce both snippets using Less 2.6.1, as reported with WebStorm. Compare the generated CSS and trace the relevant compiler behavior; done means the differing results are explained and the reported scoping behavior is corrected or documented with regression coverage.