My approach for a Jam with a long development time like this one is to make the game public before the submission deadline in the hopes that some of my few followers try it out and leave feedback/find bugs to help me make it better.
For example my submitted 1.0 release was missing a lasergate that blocked the player from completing their final objective before they defeat the final boss, meaning the boss would be awkwardly wandering around in the final cutscene. I'd reworked the map before deploying and simply forgot to bring the gate back in, and was so used to beating the boss before moving on I missed i in my playtest. Luckily Kazuki_T126 was kind enough to give it a go, and to take the time to let me know about the issue so I could fix it before the deadline.
I guess some devs may not want to 'show their cards' before the deadline, but in my experience it just makes my games better.
This is a good question though, I've always just assumed it was OK to make the game public and continue to improve it right up to the deadline; hopefully I'm not mistaken!