In a nutshell I have always perceived that when an Executive Club lounge is open in a Hyatt Full Service hotel good or bad that is the offering period
for the Diamond breakfast benefit.
If it is an overly crowded lounge with no place to sit or the offerings are unusually poor I might ask for an exception with an alternative option
which in some very rare occasions has happened.
Some concerns/situations are not in the terms and conditions and fall into the gray area and are simply unscripted.
One must be fair to the hotels and the hotels in return in a perfect world should be working towards pleasing their frequent elite guests especially
if there is any kind of deviation from the normal terms and expectation.

If I understand this correctly the Park Hyatt Melbourne is offering in addition to Club Lounge access when the club is open a full buffet breakfast
for an additional 8 dollars per day per person?
I consider that to be very fair. Now if the lounge is closed for any reason I would expect not to pay any upcharge at all and to receive my choice of buffet
or the ability to order off the menu within reason in the restaurant as well as receive bonus points for a closed lounge.
Hopefully with my lack of sleep last night I have understood the scenario above and have shed some light on topic
Cheers