A fun problem on a Mac is that if you're using APFS for your filesystem, if it fills up, you can't delete any files. It's caught me out a handful of times, and each time, the only way to recover is to reboot, and thankfully I've had more free disk space after a reboot.
I'm not going to try to understand the logic as to why APFS requires free space in order to delete files (via any method, including dd)
Probably because it's a log-structured file system, and those _really_ don't like running low on free space.
They work by appending to the log then compacting sometime later, not modifying things in-place. As such, you always need a reasonable supply of free blocks so this can occur.
I'm not going to try to understand the logic as to why APFS requires free space in order to delete files (via any method, including dd)