Oh, El Crapitan is definitely still crap. It has many issues: including, but not limited to, trackpad bugs, audio bugs, bluetooth issues and display freezes.
If I knew for sure that the newer OS would fix these issues, I'd prioritise updating sooner.
Anyhow....your new version worked. I did notice the GUI kinda lagged for a bit while resizing, and the process took about 50 minutes; but maybe that happened last time as well and I just didn't notice? I wasn't sat here staring at it all the way through, so...
Again, thanks for fixing this. There's a massive shortage of software to snapshot Raspberry drives. Balena Etcher is great for writing them, but doesn't support reading. HDDRawCopy is great but only supports Windows partitions. So having a similar program that understands ext2/3/4 is awesome.
Incidentally...does ApplePIBaker shrink FAT32 partitions, or just ext? Does it understand NTFS at all? In short, should I only use it with Linux drives?