Local exhaustion can enhance certain adjacency effects ("edge effects") at tonal boundaries. This can increase apparent sharpness. With a general purpose solvent developer such as HC-110 these effects are maximized by diluting the developer and increasing the amount of time between agitation cycles. There is nothing unique about HC-110 when it comes to these effects. You can do this with D76 etc.
This is exactly how Rodinal works, although Rodinal will not be exhausted it is the formula and the minimal agitation used during the development stage that creates the effect.