If you stare at the government's site https://coronavirus.data.gov.uk/ hospital admissions seem to have levelled off, and maybe deaths are levelling off but it's too early to be sure.
People get infected (and begin testing positive) first, then some of them get sick (a few more will seek a test and be positive) and then some of those seek hospital admission or call for advice and the advice for their symptoms is "get to hospital" and almost all of the people who eventually die get admitted to hospital first, in some cases dying after weeks of attempted care.
I think there's room for some pessimism without going so far as your parent poster, cases may be down but not as much as it seems. Lots of people seem to have gone off around the country on holiday which seems crazy to me, but clearly didn't make things much worse. People can choose not to seek a test while they're alive, but corpses have no say in what the post mortem data says.
But hospital admissions usually lag behind the number of infections. If in a week or two admissions are still going up while the number of new infections drops, then this theory may be correct.