We understand your concern about lounge access.
However, as per new enhancement, if you avail upgrade on departure option by redeeming Qmiles/Qcredits, you may access the lounge as per your original class of booking but you are entitle to access lounge as per your privilege club tier and eligibility.
If your booking is upgraded in advance by redeeming Qmiles or Qcredits by contacting via email or on phone, you may avail the benefits as per the changed class of booking (Business or First).
I just don't understand why. What difference does it make to QR whether you upgrade in advance or on departure?