From reading the media coverage (yeah I know, not the most reliable source) it seems that he had a stent fitted in July, and wanted to travel for a wedding in August. He then told his travel insurer that the stent was fitted in June.
From what I know, the recommended time before flying after surgery, as advised by the NHS can be anywhere from a couple of days to six weeks - for a lot of ops it's perfectly safe to travel before then, but insurers work the numbers. They know that if a complication arises at 35,000 feet or a foreign country then the bills really start to mount up.
The figure I've seen regarding cardiac problems/surgery is six weeks - before six weeks they'll cover you, but after six weeks the premium will be considerably cheaper.
The issue the insurers have to deal with is a) did he make a genuine mistake or b) did he falsely state the date of his operation to secure a cheaper premium.
If they required him to provide any supporting documentation, release paperwork, fit to fly letter etc then the date of the op would have been evident and it should have been treated as the former. If they relied solely on the insured's statement of health then, unfortunately for the family, they'll have no option but to treat it as the latter.
Another salutary reminder why it is important to be totally frank and honest with your insurance company.
As regards the hospital, well they look at his body as an asset, thats all. They want paid and as distasteful as it is, they have every right under Turkish law to keep hold of it until someone pays their bill. Given the public reaction though, they'll probably give in and release it after a bit more huffing and puffing - or the insurers will work something out.
JF