Personally I would doubt they would even need to justify the job role being different. The role did not exist the day after you left, but there were similar roles available in a few months time.
From my own experience Consultancies tend to use any downturn to let go the people they do not want to keep rather than the people who are not currently chargeable and “on the shelf”.
In the past I have experienced people being taken off big projects with key clients to be made redundant (literally walked out the door) which made the clients furious. The client then took the same personnel a day later on contract.
My experiences are no doubt tainted by Partnerships where the focus on cash flow is probably higher than other companies.
Good news you should get a very handsome payoff?