Freight only pays avoidable costs , and could never , ever justify a stand alone line.
High Speed transfers shed loads of capacity off the West Coast main line (trust me , I have both managed operationally the latter , in part) : and been heavily involved in planning the 2004 onwards increase in faster trains on the existing line. It took about 3 years of very stressfull planning to get the compromise timetable , up until COVID knocked back the train services.
The thing about the HS2 , when there , provides a lot of extra capacity for freight , and importantly better regional and local services , not just for London but quite a bit further out. Extra long distance calls at Watford Junction for example (impossibe at the moment , and nice to have increases in services like Watford (and north thereof) to Clapham Junction and South London. The latter is hourly at the moment , but could become half hourly. Etc.
We all want to see less HGV's on the motorways after all.........
The uninformed media , say that HS2 is only for expensive flows , - but the actual commercial model for the French is to provide affordable , high volume trains on the HS lines , ditto the Germans , Spanish etc. Big , long trains take a lot of passengers and it is imperative to fill them.