"A security incident" is a nicer way of saying "security breach" once you run it through legal counsel.

The article you're reading states...

"We took comprehensive steps to _contain_ and eradicate unauthorized access"

That's a breach my friend.

For context: https://news.ycombinator.com/item?id=46065585 OpenAI's announcement and https://news.ycombinator.com/item?id=46065208 CoinTracker’s

Well OpenAI say users' names, emails and locations have been divulged, one of them is going to accept there was a "breach"

It says "customers were impacted" and that they had to work to "eradicate unauthorized access"

It's just a very weazel-worded disclosure. Most definitely a breach.