I still don't get the point of this X900.

It would be much better to do a Fellgate -> Simonside -> Tyne Dock -> Chichester -> South Shields service instead imo which would only take 40 minutes or so from South Shields to Newcastle, rather than sitting on a bus meandering around everywhere especially for those at Tyne Dock and Chi which don't have anything express at all and are both quite busy stations.

The time wise to Newcastle (where most people no doubt go) would be barely neglible for most the stations compared to normal since the Metro meanders around the world through Jarrow etc usually. Metro takes 28 minutes. Rather than having to sit on a bus for 36 minutes, which will no doubt take longer as it'll be congested between Jarrow and Heworth as it always is.