Dunno. I presume it's that COVID-19 is the reason for admission, but that is an assumption. Doesn't make that much difference to the basic message: nobody (sane) thinks that getting infected with this thing is good for people, after all.
You can see bother measures of deaths from COVID-19 on these graphs:
https://coronavirus.data.gov.uk/details/deaths?areaType=nation&areaName=England
The "within 28 days of a positive test" was always just been a nice quick way of producing a statistic. It happens to pretty much match up with the "on the death certificate" measure earlier on, but less so now (with our immunity we've allowed the virus to spread largely uncontrolled and it's much more likely to die of something while having had an incidental infection, though it's also less likely you'll have tested at all).
(There was also a bit of misinformation suggesting that the number of people who'd died from just COVID-19 was very low, but that was mostly a (deliberate) misunderstanding of what goes on death certificates.)