What of the percentage of these 3.9 million women who actually don't want to retire at 60? When I was younger my mother knew lots of women forced to retire at 60 who were devastated to lose their jobs when they wanted to stay on. My neighbour just missed the deadline and now, although she has a good works pension and State pension, is bored stiff, misses her work colleagues to the point they all go for a drink (before CV-19) every week and is desperate to find a job, any job to keep her occupied. To be 60 in 2020 is much different from being 60 in 1970. I agree with the decision, and although I've paid in 35 years to my pension (some not full as I was not in the UK) I still think 66 is a fair age these days.
There are jobs, however, where expecting anyone, male or female, to do the job to their full ability at 66, is unreasonable, but I think these jobs are taken care of by private pensions being available from 55. Remember, N.I. contributions are not just towards your pension.