Because you missed the original distinction, which is that an annuity — a product purchased using your pension savings where all the value is lost when you die — is not the same as other pensions, where for example you have stocks and shares paying dividends, in a pension wrapper, and those pass on to your estate when you die.
The word pension is overloaded. A SIPP is a pension, the state pension is a pension, and people refer to their annuity as pensions too.
> A pension is not a fund. A pension fund is a fund!
The word fund is being used in two different ways here. A pension is a fund, but is not a Pension Fund.
The wikipedia page you mention says that "The common use of the term pension is to describe the payments a person receives upon retirement, usually under predetermined legal or contractual terms."
I'm familiar with retirement accounts and pension plans in a number of countries but not in the UK. I see that in the UK "pension" is often used a short-hand for "pension scheme" (it seems a relatively new development which I've not seen reflected in dictionaries).
For what it's worth, the wikipedia page for Personal_pension is redirected to Personal_pension_scheme: "A personal pension scheme (PPS), sometimes called a personal pension plan (PPP), is ..."