Generally, between 10% and 13% (fluctuates in the past few years) of Bitcoin is held on exchanges. This Bitcoin is probably fair game for 6102s.
Gold is wayyyyy worse though as far as custody centralization.
People talk about the Blackrock ETF as a centralization risk, but I see all Bitcoin not being self custodied as basically 6102-able anywho. Don't know if it will change the percentage much (though a decent price increase will naturally cause more people to take profits; last bull market being cut short by the China mining ban and the macro climate caused a dampened NGU) This may pull some more coins out of self custody (Unfortunately). But what's pretty crazy is that a few weeks ago, coins on exchanges were at 6.4%(!) Just because of all the SEC stuff, and people wanting to get coins off exchanges. Soooo. Who knows.