Hey folks - The linked issue was a separate bug, this one looks like a change we shipped yesterday to appropriately enforce public app access to Business and Enterprise plans since we've been seeing a bit of abuse around that lately. Not from your apps, but it seems like existing Free and Team plan public apps got caught in that check.
Think the feature has always been part of those plans as long as I've been here, there was just a longstanding bug a while back where we didn't always prevent creating them. And while recently investigating phishing reports, we found we didn't enforce after downgrading plans.
While definitely not an intentional change of behavior, we're following up on how we should balance these cases against the ones taking advantage of the functionality on our side today.