A reduction of 40% of a 12 hour journey makes sense that is about 5 hours. But a 401km project to reduce the travel time by just only 1 hour doesn't make sense.
How fast do you expect a 401km long project to be able to travel, considering this involves an underwater tunnel and other associated difficult terrain.
That's a transit speed average of 267km/hr, which when considering acceleration and deceleration seems reasonable to me for high speed rail.
If you want a 12 hour journey to be reduced by 40% the time of the journey will still be 7.2 hours, and considering the transit speeds of high speed rail (let's say averaging 267km/HR) you'll probably still need to build some 1922km of rail if it is of equivalent geological complexity to this project.
So yeah I suppose if you're reducing a 12 hour journey to a 7.2 hour journey, then that is reasonable but you'll still need to build a project over 1900km long.