You really are being far too faux intellectual about this.
It was a great piece of skill that played a teammate on goal against a defence already in place around their area. The way he held it up in order to time the pass and fixated the defender in one fluid movement was inspired and a lovely example of footballing joy.
I personally don´t even know where KdB was supposed to move in this scene.
Drifting outside towards the corner flag would have created an additional passing option, but given the angle, distance towards the Goal and time it would have given the defense to prepare it would have certainly been a worse one than the centrally positioned Sterling or Bony in the left part of the box. Defensively it would have been worse as he would have broken formation and made a potential counter situation (created by a misplaced pass for example) over his side more dangerous by being behind the defense instead of standing in the way.
Drifting centrally would have occupied the space Sterling was standing in and unneeded while creating defensively the same problems as the first option.
Following Silva inside the box would offensively made just as little sense as the Spaniard would have been forced to turn or play a back heel pass.
All in all, De Bruyne keeping position was actually the right decision in my book as it increased the chances of getting a rebound ball or stopping a potential counter as he was the only City player in that area.
I´m all for a lot of off the ball movement, but said movement actually has to improve the overall Situation. This is not such a case.