They can borrow against etf holdings at better rates than they can borrow against bitcoin collateral so I am sure some of this is occurring. Maybe not entire stacks. I also think 100k was an area a lot of early adopters planned to sell some. And I think the last bear market was much deeper than we all expected so a lot of bitcoiners delayed purchases to stack more sats. Now that the price is elevated there is a good chance they are selling a bit to finance the stuff they held off on buying during the bear.