Though Concourse isn’t entirely duplexed; ⅌ https://mbtype.com/pdf/concourse-type-specimen.pdf#page=7 https://mbtype.com/pdf/concourse-type-specimen.pdf#page=7:

Though Concourse isn’t entirely duplexed; ⅌ https://mbtype.com/pdf/concourse-type-specimen.pdf#page=7 https://mbtype.com/pdf/concourse-type-specimen.pdf#page=7: > Duplexing. In type, duplexing means matching the widths between styles so that each character occupies the same space on the page. This way, you can easily change the weight and style without affecting your layout. In Concourse, weights 2, 3, 4, and 6 are duplexed to each other. (For this reason, the three lighter weights all use weight 6 as their bold style by default.) Every italic is also duplexed to its roman, including weights 7 and 8. So yeah, all normal use is duplexed, but it has a couple of extra-bold weights that don’t fit that way. This also draws attention to the other area you may want to think about this with: italics. Definitely depends on the style; broadly speaking, serifs won’t want to duplex their italics (they’ll most commonly be narrower), but sans-serifs might.