As far as I know JWs don’t use the phrase “heart condition” any more. That’s old terminology. Where are you getting the idea that survival is based on “heart condition”? Is it in the latest statement and Watchtower and I missed it?
What the statement said was that an unbeliever at Armageddon has the same chance as an unbeliever being resurrected. Since JWs have long believed that billions will be resurrected (the Reasoning book speculated that the earth could cope with and feed 20 billion) it is reasonable to wonder whether the recent statement really implies that billions will survive Armageddon. If that’s not what they meant, or if they backtrack, as it stands it is a reasonable inference from what they have said.