Apparently this well known bug still unsolved! Unbelievable and unacceptable.
I just purchased an "ASUS Dual Radeon™ RX 7900 XTX OC Edition 24GB GDDR6" and when you connect the third monitor, the memory clock remain at full speed and the power consumption at IDLE go from 20W to 90W.
Same issue regardless I use DP or HDMI output.