This problem goes beyond Fitbits. I have a Garmin Forerunner 220 that will not connect to my S5 after the aforementioned update, but it WILL connect to my Nexus 7, so the problem is not the watch. Additionally, I have a scale that refuses to connect to my S5 after the update. Neither device had any connection issues prior to the update.
The problem is unlikely to be anything except the update. Between your devs and Samsung, please get it together and fix this. In the meantime, please make the prior update (G900VVRS2DQD1) available so we can (hopefully) use BLE.