If itch.io allows you to add additional files as a separate download to that game's page, but doesn't count it as a submission to the Game Jam, then sure. The only thing is to make 100% sure that itch.io, and thus the judges, don't see it as you trying to get around the lock after the submission period ends, as that will disqualify your entry.
In other words, exercise caution regardless, as we'd hate to see you get DQ'd just because of a technicality.
What about this kind of case? Putting link for a bug fixed version in game description. Not to get around the lock, but give other people to play the better playable version
(Reposting from your other question, which was essentially the same...)
As long as you aren't altering the main download, the one you submitted, you're fine. The judges will only play that download, not any addendum or other files on your page. The only way you'll get DQ'd is if you manage to change those submission files. Adding additional links for players who aren't the Judges is fine. :-)
