Yes and no. Before, FP return times did not commence until around 10:00. So people who arrived at RD had a full hour to ride SB before the first FP returnees entered the line. With FP+, times are available to be booked the second the park opens. So with a really popular attraction like Elsa and Anna, those times will be booked solid. Given the fact that many people on that thread are not getting any times whatsoever, it is fair to assume that the times when the park first opens are fully booked. When the FP times are fully booked, there really isn't any room left for SB people to filter in. Even if there is, it will be dribs and drabs. I would imagine that anyone who gets in the SB line for E&A 15 minutes after the park opens will be looking at a 2 hour wait. So yes, some RD people will be able to rush to the attraction. But only the very, very first people have any hope of beating a 2 hour line.