actually i think the recall might have to do with this..
each season an otherwise waiverable player may be recalled form the minors to replace a guy who is on the IR and not be subject to waivers when sent down, as long as he is sent down at the same time as a player is activated from the IR. However, an one player can only do that once during a season and be exempt from waivers.
i do believe fiddler was recalled when nichol was put on the IR, and then returned immediately upon Nichol's activation back to the active roster. If this clause was used, fiddler used his one recall without having to clear waivers to return to Milwaukee.
Now Hall and Walker are placed on the IR and Smithson is recalled at the same time. If the waiver rules here haven't changed (and who knows anymore?), smithson was eligible to be recalled and not have to clear waivers to be sent back as long as when he's recalled solely because of a player placed on the IR. (this one time for him like fiddler)..