I'll agree that it does seem unusual. The Business Class check-in at Singapore is a bit of a unique one, and I understand that only Platinum QFF card holders can access it, no luck for Golds or Silvers. As for no priority queues though, it does seem unusual, every time I've been through Singapore there's been a couple of counters open opposite the main row of Economy Class check-in's, marked for Qantas Club, Silvers and Golds (and oneworld equivalents). The check-in staff have always been reasonably accommodating there too with requests for blocking seats off and the like.