I think it is pretty clear.
It only impacts whose who reach state retirement age later than April 2017 (at the earliest - could be set a little later). All those reaching that age before the date will receive the old amount plus any SERPS, and S2P that they may have accrued.
If one reaches state retirement age after the infamous date, one gets the new amount - £144pw in today's money. If one would have been entitled to more than this amount because of additional SERPS or/and S2P elements, one still gets the enhanced amount - the point is no-one gets less than £144pw.
Those of course who lose out are those with a little bit of SERPS who now find themselves getting the same amount as those couldn't be arrised to save earlier (and end up with Mr/Ms Thrifty).
The moral of the story? - never, ever trust any Government to stick to what it said when it comes to pensions.
Me? - I just make sure I'm not putting any more (through NI contributions) into Government coffers prior to me reaching the state retirement age - as I've already got my minimum 35 necessary years, thank you very much. I can only urge others to do likewise, where they can.