namcap does not distinguish java class files from Mach-O files since both use the same byte magic CAFEBABE. See FS#34300
Implementing this would only need a test if the value of the byte at offset 7 is greater than 0x30. See: https://github.com/file/file/blob/master/magic/Magdir/cafebabe
I think having Mach-O files in a package is a _very_ rare case. But on the other hand implementing would be no big deal.
Would a patch for this be accepted, or is it not worth?