It's probably more cost effective to melt-down the mono's than sell them... or just pretend there is no such thing as a second and sell them per usual.
I have a pretty good idea why but last time I mentioned anything about it I got flamed pretty bad. I did a project there for my operations and production management class in MBA school. I do use more of their bullets now that they offer a tipped version. They claimed that they sent the seconds back to their copper supplier to be remelted. I haven't been to their new location and things could have changed a bit since I was there so.....
They can recycle the monolithic copper bullets for meltdown because there is no lead core to deal with. Recycling lead core bullets probably wouldn't be as economically productive as selling as seconds due to cost of dealing with lead separation and toxic materials regulations. At least that's my guess.