Absolutely, but unless I am mistaken, this is then entirely unrelated to a 'SFU' note or absence thereof, so from the point of view of the OP's question, SFU+non overbooked flight makes no difference.

In fact, my suspicion is that SFU notes make little to no difference anyway as upgrades are increasingly automated and when they are manual, are typically decided upon by the station manager or flight manager who probably have their own rules for priority. I may be wrong of course.