Yuval, thanks for your response. Totally agree that neither model is permissionless in the bearer sense, and that KYC/AML constraints apply regardless of issuer or DTCC.
Where I still see a meaningful difference is not whether DeFi-style interaction is possible, but how much

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BitMEX co-founder Arthur Hayes wrote that the recent Bitcoin crash may stem from traders' concerns about IBIT (BlackRock) […]
The article, "Arthur Hayes Speculates on BTC Crash Cause: 'Institutional Hedging Operations': IBIT Options Explode $900 Million," was originally published on BlockTempo, the most influential blockchain ABMedia media.

Arthur Hayes speculates that the reason for the BTC crash is "institutional hedging operations": IBIT options saw a surge of $900 million.

Unusual trading in BlackRock’s bitcoin ETF, iShares Bitcoin Trust (IBIT), has led traders to speculate that this week’s sharp Bitcoin drop may have been triggered by one or more Hong Kong–based hedge ...

Bitcoin Selloff Sparks Hedge Fund Speculation Around BlackRock ETF

Bitcoin ($BTC) has recently gone through a sudden shift on Bithumb, a well-known South Korean crypto exchange. In this respect, the $BTC/KRW trading abruptly plummeted over 10% below the worldwide ave...