It probably shouldn't have been in stretch, but as long as it does not cause trouble, you can let it rot there :-)
Agreed that it shouldn't have been released in stretch; at the time I had the idea of supporting it through backports. Given the relatively low popcon statistics and activity in bts, I think I prefer to just leave the package in stretch alone for now. If anyone is caught out by the situation later I can proceed with the patching and removing as outline above.
Carl