A bit late to the party, but I just tried #12653 and noticed some non-intuitive behavior (on macOS), that's probably worth explaining release notes and help.

Before this new feature I kept the entire datadir on an SSD drive, so I launch with: `bitcoind -datadir=/Volumes/SSD/Bitcoin`.

Initially I naively moved `/Volumes/SSD/Bitcoin/blocks` to `/Users/bitcoin/blocks` and added a line to `/Volumes/SSD/Bitcoin/bitcoin.conf`: `blocksdir=/Users/bitcoin/blocks`.

I then realized that I shouldn't have moved the `index` subdirectory, so I moved that back to `/Volumes/SSD/Bitcoin/blocks/index`. Having an empty `blocks` dir with just and `index` subdir is a bit weird. Perhaps after @jimpo's #11857 is merged, we could just move / assume all indexes to be there (if `-blocksdir` is set)?

Worse, it created a directory `/Users/bitcoin/blocks/blocks`, which seems like a bug. I had to set `blocksdir=/Users/bitcoin` instead.
if (pcoinsTip != nullptr) {
        FlushStateToDisk();
    }
    
    
    GetMainSignals().FlushBackgroundCallbacks();
    
    
    
    
    
    {
        LOCK(cs_main);
        if (pcoinsTip != nullptr) {
            FlushStateToDisk();
        }
        pcoinsTip.reset();
        pcoinscatcher.reset();
        pcoinsdbview.reset();
        pblocktree.reset();
    }
    g_wallet_init_interface.Stop();
#if ENABLE_ZMQ
    if (g_zmq_notification_interface) {
        UnregisterValidationInterface(g_zmq_notification_interface);
        delete g_zmq_notification_interface;
        g_zmq_notification_interface = nullptr;
    }
#endif
#ifndef WIN32