I haven't tried to complete it since I plan to travel that ticket, but I wonder if the advertised policy is a 25% penalty, but the system is coded to allow the cancellation to a voucher without fees at least through September 6. I've booked a few during this sale, so I'll see what it shows on Friday if I try to go in and cancel it.
Following up on this: when I go in to cancel it, it shows that I'll get 100% of the ticket value onto a voucher. Of course, Amtrak may change this at any time (and their stated policy is that it should pull a 25% fee from that voucher) but at least for now it looks like they can be cancelled for a voucher without penalty. I also haven't completed the cancellation process (because I want to travel on these tickets still) so it's possible that it slips in at the last second.