Switching between two fonts in different circumstances seems like less of a hack than embedding some kind of Virtual Machine into your font engine with all the security issues that follow.
It's totally possible to create a safe virtual machine for specific uses. There have been many attack vectors for fonts over the years due to the complexity in parsing them. I do not recall any of them being due to the hinting language.
The Mac one is hard coded for a single OS and font combination and a specific size down in the operating system.
I disagree that the later is less of a hack.