Wrong place

In July 2018, Transport for the South East, in charge of researching and developing plans for our area, released a review called Economic Connectivity. Buried at the back, a map showing estimated traffic flows on major roads in 2040 - i.e. after the current £75m-worth of improvements to the A27 between Lewes and Polegate. It shows the current, partially single-carriageway road as having 'moderate congestion' in the morning peak. There is severe congestion predicted for the Lewes by-pass, from Kingston to Southerham, and regular congestion beyond Polegate. So why not spend the money there ?  Why spend £450m on a dual carriageway to alleviate 'moderate congestion ?