This is true. They had a template with the Manchester Commonwealth Stadium of how to make it work, but unfortunately arseholes like David Conn whinged dismally about private interests benefitting excessively from the public money spent on the stadium.
As a result, Culture Secretary Tessa Jowell and London Mayor Ken Livingstone took a decision that the stadium would be scaled back and retain the track. This was entirely a political consideration aimed at ensuring that a wealthy Premier League club wouldn't move in. They complacently assumed that they'd be able to rent the venue in winter to Leyton Orient or maybe one of the London rugby clubs only to discover that, just like the bigger football clubs, these outfits had no desire to play at a stadium with a track, either.
I confess to loathing Boris Johnson, but when he became London Mayor he quite correctly identified the proposed legacy of the main Olympic venue as a joke. He alighted on the wrong solution, however. Spending north of GBP 300 million to convert a venue so West Ham could take it on a 99-year lease at an annual rent of GBP 2 million was a really poor deal for London's council taxpayers. It should have been knocked down after the Games and rebuilt, as Spurs proposed.