Bitcoin is not Fungible.

I learned today (although this is not new) that bitcoin is no longer fungible in that there is now clean bitcoin and tainted bitcoin. Each have a different price. Can you help me understand this? I am realatively new to BTC.

My understanding is if a any bitcoin flowed through a wallet even before it came into my ownership it may be tainted (by suspicion of the activity of a flagged account). Banks want to lend only on BTC that had never left an exchange as it doesnt need to be audited. If the BTC has left an exchange then they have to go through a process to see that no part touched a flagged wallet at any part of its journey. If my bitcoin goes up I will want to borrow against it I wouldnt want to pay CGT.

Institutions including MSTR wont and can't buy tainted bitcoin as they are regulated.