The memory junction temperature was just added to HWinfo like two or three weeks ago.  You need at least version 6.42 to see that on the 3000 series cards.   
I have an Aurora R11 with RTX 3080 and HWINFO is not showing a memory temp sensor on the card. Is this correct? (RTX 3080-up cards should have one from what I read) 
Aurora R11, OEM RTX 3080, no memory temperature sensor?