In practice, the best way to handle a drive that might actually need to be resistant to that level of analysis is to degauss the drive, shred it, and then melt

In practice, the best way to handle a drive that might actually need to be resistant to that level of analysis is to degauss the drive, shred it, and then melt it down in an incinerator. You wouldn't mess around with Gutmann at all because it's just a poor man's degauss, used for situations when you don't want to risk damage to the drive. You wouldn't just detonate the drive either because, as you mentioned, individual pieces could potentially still have recoverable data.