Which they do seem to have some point about from around 2005 onwards (ish) it would seem that DWP just stopped thinking about it in any concrete way. Which is hardly surprising, whilst the Home Office is probably the most dysfunctional government department the DWP are not far behind. So I do have some sympathy with them, however, at the same time if these women were relying on their state pension to make up a significant portion of their income from when they turned 60 it seems staggeringly complacent to, seemingly, not do any checking about their state pension entitlement (which would flag up the upcoming age issue to them) until, seemingly, they were months/weeks away from turning 60.
The change wasn't hidden away from them, the Pensions Act of 1995 provided for the change to be rolled out between 2010 and 2020 and the Parliamentary and Health Service Ombudsman themselves determined that until 2005 DWP communication was of an acceptable standard. So it wasn't a state secret! Now again, I do have some sympathy with those that got caught up in the acceleration following the Pensions Act 2011 which saw the equalisation to 65 brought forward to the end of 2018 and then increased to for everyone by the end of 2020. But again, none of this was secrete!
At some point there has to be some level of personal responsibility for making retirement plans. I think the DWP, across multiple administrations, have not done a good job informing people of the changes. The critical failure seems to be in 2005 when they knew that many women weren't aware of the changes and then didn't really do very much until very late in 2007 early 2008 which of course would only be a couple of years from when the increases would kick-in. But, at the same time I'm not sure that the Government owes compensation to these women either, particularly not when the compensation will need to be funded predominantly by working age taxpayers who are facing state pension ages far in excess of what many of these women had. My state pension age is 68 (full expecting that to rise further). Older even than many men let alone women from bygone years!