Does this study assess the long term cost of software? It may be true that this has little benefit in writing code from scratch, and my experiences are that TDD

Does this study assess the long term cost of software? It may be true that this has little benefit in writing code from scratch, and my experiences are that TDD definitely takes longer when writing code than not doing it. But, how does it evaluate claims that 90% of the cost of code comes in the maintenance, not the initial creation of it.