OK... let's assume this to be true. Let's assume this helps ease rail congestion along the path of HS2 and the bits alongside it. What about the rest of the country? The lines into London from all other directions, especially the southern sides of London are even busier than the route he's talking about. We passed the point many years ago that if humans had the same transport laws as animals then the train companies would be prosecuted every day for overcrowding.
We'll be spending £40bn or so to create a nice little clean-spot on the network for a few years while the rest of the country has to put up with what they've already got.
A friend who works for National Rail, in the track-side maintenance management chain, said that they'd be far better just building more standard lines to take freight, move freight off the passenger tracks and you can almost double the trains on it quite easily. Also, creating a dedicated freight trunk could remove a lot of HGVs from the country's motorway spine. Not as sexy selling a freight trunk though as it is a 225mph bullet train network.