Rigs drill for oil; Platforms/FPSO's produce, process and transport it - Don't worry, after 40 years of UKCS Oil & Gas operations, the BBC continue to make this mistake!! (everything is an "oil rig")
9m sea is rough but she (and all platforms) are designed for 30m (aka "100 year storm"). Though, as you say, an interesting winch ride.
I'm sure she'll be fine, there is redundancy in the mooring