Agreed. I come from the FLOSS side of things, for me it's natural to release sources. And while in the FLOSS space, we disagree on different licenses, we agree that source releases, with a proper license attached to allow for re-use, is important.
And "release early, release often" is also a common mantra: things might happen, so while we wait for a drop of perfectly finished and cleaned up sources, maybe you get hit by a bus. Or, less crass, your HDD dies and you don't have any backups. Or something else catches your interest or your RL gets bogged down or a global panini hits and your headspace is just weird as all f. It happens, that's okay.
Don't get me wrong, good documentation and detailed documented specs of file format is also important. Ideally, there's both docs and code. With code, though, if you can get it to run, you can immediately see if it's correct.
This isn't meant as an attack or rant or anything, just for an explanation of where I'm coming from here.