Thread creep again....but
I think we have to recognise that the Forger layout was chosen as a stepping stone to the Freehand primarily to give service experience of the config necessary for a supersonic vertical lander.
They knew it would never compete performance wise with the Harrier but they had their sights set on the future.
The Harrier was a truly subsonic aircraft. The concept of a single engine at the CG was not the best one (to put it mildly) if the engine was a supersonic one and so taking in a modest mass flow but giving it a huge V.
The subsonic Pegasus was perfect to get VSTOL launched with the simplest possible config. It allowed the aircraft to have a good operating site flexibility just because it takes in a huge mass flow and gives it a modest V which is kinder on the airframe when it is washed by the efflux.
The F-35 has the best of both worlds hot and fast at the back (but out of the way of the intakes and airframe) With plenty of cold and slow at the front to block the hot stuff moving forward into the intakes. Which is doubtless why it won…...?