Not sure that is true.
When you have a high speed train, going from the centre of a city to the centre of another city... and can subtract time to get to airport, time in airport security, time to wait to board a plane, time to taxi, time to circle before landing, time to get to the city, time to safety margin most of the above... the train comes out at least comparable on time (not an order of magnitude off), cheaper, greener, and centre-to-centre.
For me... European trains are so nice in comparison to flying that unless there is a time penalty of more than double to triple the real time spent flying (which in this case does not feel true)... then the train wins.
It's also a very productive journey. I can't do meetings on a train, but 6-7 hours uninterrupted in a comfy chair with power and internet is still coding / making slides / etc.