Replying to myself because I think people are overreacting to the last paragraph.

There is a case to be made that BTC spot and future are not delta one. I did not check specifically for BTC, but often in crypto the liquidity on futures is much higher than on spot, which makes the futures market much less sensible to market manipulation, flash crashes, whale dropping, etc.

Holdings are also much clearer and easier to assess for regulated futures than for spot.