Just looking around the internet and seeing people with fritzboxes saying they couldnt get online when g.inp enabled, plus the post on sky saying they couldnt get online with a dsl-ac68 also (that guy got online after disabling g.inp in the dsl-ac68 settings), this matches the explanation given by openreach stating the rollout had to be rolled back due to ppp sessions refusing to connect.
Yet even tho many more people will have devices like the openreach modems and homehubs, I couldnt find a single person using either a sky hub, homehub or hg612 not able to get online with g.inp.