I understand how you must feel. I'd probably not be happy about having a waymark declined after having been approved years earlier.
For cases where a category description is updated and previously approved waymarks fail to meet the new requirements, I think grandfathering is appropriate. But in the case of Border Crossing category (at least as I understand it) the only waymarks that were changed from approved to declined were those that never met the original requirements, and still don't meet the new requirements.
The situation is unfortunate, but I think the decision was arguably the right one under the circumstances.