I was also decidedly bullish initially (on the exact same grounds that you're describing), but I'm increasingly aware that this can be flipped the other way too

I was also decidedly bullish initially (on the exact same grounds that you're describing), but I'm increasingly aware that this can be flipped the other way too. For example: let's say the BTC futures price is lower than the exchange price, and let's say you hold BTC; pursuing an arbitrage, you buy cheaper futures, sell BTC to make arbitrage profit; multiply this across many self-serving market agents, and you have market forces working to eliminate the arb opportunity: there's our transmission mechanism, regardless of how the futures are settled.