1. OANDA didn't move gbp/usd - it could have gone either way. They just provide the opportunity to trade it.
2. OANDA are not responsible for positions their clients take.
3. OANDA's spread policy is transparent. It's also sometimes painful and equally at times hard to justify - from a client perspective.
But being aware of how they operate their dynamic spreads and their published historical data on max spreads, it's not a major issue to navigate safely. They're not too bad and their operational platform is fast.
As much as I dislike dynamic spreads, if it's that or no fills, slippage and inexplicable platform disconnects - I'll go with the devil I know and can factor in every time.
Your screenshot is from a third party and not OANDA themselves.
As I said in response to your post in the other thread, OANDA hasn't been above 4.2 this morning on gbp/usd and typically under 2 pips.