Three people can hear the same rumor that started with one source. I doubt it's anything but Alberta Springs because I don't know of anyone who was making 100% rye ten years ago in sufficient quantity to supply even a small brand. The best available evidence now says it's still Alberta Springs. I do, however, note that Alberta Springs is owned by Beam, which may make a 100% rye at Clermont as a blending whiskey for its own house blends, such as Beam's 8 Star.
That doesn't necessarily mean Beam is selling the Alberta Springs whiskey to Zoeller and Pickerell. There could be an intermediary involved. But Beam is known to sell some bulk when it needs to adjust inventories.
Although no one has confirmed that Alberta Springs is the source, it is known that rye is the only grain they use, so it's a good bet. Gimli, Diageo's plant for Crown Royal and others, makes a 100% rye, but I haven't heard they're selling any of it as a straight and they're unlikely to have any in surplus. Forty Creek makes a 100% rye, but they're too small to be supplying anyone else. And, of course, with the exception of my Beam theory, those are all Canadian sources.