Back in the day before hidden cables were invented, it was a thing for some time trialers to force the cable through the housing of a standard lever and drill the bars to accommodate the cable. Braking would have been compromised, but as the bikes were solely used for flat TTs, it didn't matter too much - the pursuit of aerodynamics and weight reduction was the objective.
Then came this idea. A proper lever that was designed for concealed cables, but they hadn't yet thought of hiding the cables beneath the bartape, so it still necessitated drilling the bars