There's nothing in the QP T&C about members being denied access due to space limitations. Members' guests, yes, but not the members themselves.
The only thing I can find that could justify this is 10.6:
10.6 Qantas Club staff have the discretion to refuse entry to any Member or guest at any time if, in their reasonable opinion, the Member has not or will not comply with these Terms and Conditions or the Club Rules, or the refusal is necessary or convenient for the orderly operation of the lounge or other facilities or the safety or comfort of other Members, their guests and staff.
It seems outrageous if members are being denied access on this basis.