Yes, it still writes 64 bytes a scan. We really didn't make any provision to try and synchronize the frame. My experience with DMX has been lighting where it generally doesn't matter. I guess some complex fixtures might be less happy with channel data being a bit more async, but given that DMX doesn't include any form of data integrity check, it never really occurred to me to treat it as reliable.
I'm pretty sure something could be conjured up to make it possible to either take the scan hit on the full frame or make it possible to push the frame buffer while disabled, then enable to send. But no, it isn't there now.