Why isn't that still a concern?
Since Apple's market cap is now $790B, half the value is $370B, which means that even with the cash reserves, they'd be $123B short of being able to repay, and they'd need it available on day one to execute the hostile takeover. And like they say, $100B here, $100B there, soon you're talking real money.
Essentially Apple's available cash is much less than it appears.
That's certainly one way to put it.