It might be this [1] which says "According to the report, the decision was made by officials to continue to build the Birmingham Curzon Street Station to its full specification because it was cheaper than trying to cancel part of the scheme. "

"that the project will plough ahead with building a seven-platform station at Curzon Street, despite just three being required for the reduced HS2 line."

Unfortunately inews doesn't seem to quote the original NAO report, just linking to a list of NAO news items on inews :(?

[1] https://inews.co.uk/news/politics/hs2-waste-new-birmingham-s...

[EDIT] So the ft does actually link to the report [2] from this page [3] saying "The watchdog said scrapping the northern leg of the flagship high speed rail link would take three years and cost up to £100mn, and that some platforms would still be built even though they would never be used."

[2] https://www.nao.org.uk/wp-content/uploads/2024/07/hs2-update...

[3] https://www.ft.com/content/ecde4265-0269-4169-ac0e-179938667...