The problem is this story may be confused or even made up, but there are similar ones that I've heard, including from people on this forum, to make it believable. Though I thought the 500,000 figure was way too high, I did know that many other folks, including those who work in hospitals, have reported that they got something like 50,000 for the hospital for "COVID Cases," not necessarily COVID deaths.
That said, I also have heard reports here and from other people; I know about the sudden change in care the moment the hospital discovered the person was not vaccinated. Either the "we can't do anything for you" discharge or the "throw them in a ward and leave them to die" method, sometimes both - the person is sent home with no treatment, gets worse, and then is just kind of ignored or just thrown on a ventilator.
They treat people with all sorts of things that have other lung problems, viral or bacterial, but I've never heard anything quite like some of the first-hand reports from patients and occasionally staff about this issue. This is why this story is believable even if it turns out to be fiction, and it only slightly exaggerates what happened to a lot of people, some of whom did live to tell about and/or their loved ones did.
The majority of these stories I have heard (the first-hand ones) seem to come mainly from the United States, which is why I am suspicious of some sort of treatment mandate and/or monetary incentive going on. Sure, people also died shut away from loved ones, and there were a lot of rather suspicious "we expect your loved one to die today, here's the last phone call" in the UK as well; but I don't think I've heard any of the "sudden change in attitude and treatment" after finding someone was unvaccinated as I have in the US. Or at least, not in the same way; if it exists, it is being kept quieter and not made as evident to the patient or the family.