Don't think there should be any doubt about that.
zebadee, I don't think it was about your "'misplaced' conclusion", and I know for sure it's not about any "crossflashing side effect".
Sidenote. I've been on Philips 1648 2.3 firmware with my DW1640 quite many times and SolidBurn for known media has always been activated by default.
It would surprise me a lot if 1660 is any different in this aspect...