(Also technically no CC licence is an open source licence, since they don't require works to release the source code, because they aren't intended for source code)
The MIT and BSD licenses also do not necessarily require the release of source code. It is just that if you license code under those terms and pass it to someone else, then they receive the rights to do a lot of things with the code, including releasing it. I don't think that is much different with the CC licenses (the non-commercial variant is definitely not open source though).
It would be rather pointless, other than giving people the right to binary patch and redistribute the file. I'm mostly just splitting hairs because seeing CC licenses used for code annoys me.
The same applies to MIT and BSD licenses. That was my point.
> It would be rather pointless
Agreed, but nothing in the license text prohibits it in any way. Even if it did, as the sole author of some code you are not bound by whatever license you pick, even if it was a copyleft license that would require other people to share their modifications.
I think you're confusing open source with copyleft; ex. BSD style licenses are open source while still allowing proprietary derivatives.