An assumption appears to have been made within the forum. If people are talking about 400m platforms in Liverpool, they must also assume 400m trains. I agree that 200m is all that is officially mentioned.
The 400m from Crewe bodge is a nod to the concerns raised over overcrowding. This is something that HS2s own reports pointed out a number of years back. It was always bizarre that we as a country should build this new railway line, and yet one of the key cities it's meant to serve be stuck with limited capacity, let alone limited capacity that was acknowledged as being problematic. Especially contrasted to the vast over provision elsewhere.
Liverpool's traffic to Birmingham and London has boomed since then, so the issues will be known to be even more acute.
If (it's a big if) this project happens, it would be bizarre to develop a new Liverpool station and not have it developed to the highest specification, so that bodges can be replaced with normality and other missing aspects (such as trains to Birmingham) can be implemented.
The trackbed of this old LNW line has completely disappeared east of Sinderland Crossing. There would also be major conflict with Sustrans, as the route west of Sinderland Crossing is part of the Transpennine cycle route.
The bottom line is there is a good existing railway between Liverpool and Manchester - the original intercity line via Chat Moss. The journey time could be reduced to 30 minutes non-stop by using electric trains and cutting out the intermediate stop. There is no need to spend vast sums of money on an alternative route.
That assumes the purpose is simply to connect together Liverpool and Manchester.
The NPR line was an idea invented in Liverpool, as a means of getting the city onto HS2 properly. That you can use it to also create a new route to Manchester via Warrington simply adds more value to the infrastructure needed.
Warrington area already suffers a large amount of physical damage from HS2. At least this line would put its centre 15 minutes from both Liverpool and Manchester city centres, and 10 minutes from an airport.