As a GS I can tell you that I have NEVER, EVER "kicked" someone out of a F seat. Oversell protection only ever applies to coach and I've ridden in the back when F has been full at time of booking and on irrops.
Respectfully,
The GS Boogieman
I didn't necessarily see it as GS members kicking someone out of F. The flt had been scheduled as a 319 for weeks then the day before until the morning of UA switched it to a 320. By noon the day of the flt they switched it back to a 319. I think in the time it was a 320 some upgrades were processed and caused the oversold situation. I'm not positive but it is just my theory.