Thank you so much for pointing this out, Moretti! It drives me crazy when people talk about the extend feature like only SASS has it. People are always underestimating how similar Less and SASS are.

Then, in Bootstrap terms and since the grid syntax is offered in mixins, should it be used as follows

    .foo-class {
        &:extend(.col-md-4, .col-md-offset-8)
    }

instead of using the mixin?

    .foo-class {
        make-md-column(4);
        make-md-column-offset(8);
    }