Some manga volumes will credit multiple letterers on the copyright page. One letterer for the print version of the volume and another letterer for the "original digital edition". Currently, the "lettered" relationship is only available for works, but it seems like when there are credits explicitly for the print edition, it should be possible to add the lettered relationship to an edition.

In the specific situation above, I imagine the letterer of the "original digitial edition" will still be credited to the work, and only the print edition would list the print-only letterer... but I might be wrong. It's a bit of a quandary.