The author doesn’t say a billion is 100 million. They say they’d like to be able to insert a billion, and say they’re able to insert 100 million. It’s not a contradiction.
Also I got another feedback that title should indicate that it is a test database and emphasise that it is not durable.
I am wondering the right way to convey all of this in the title yet also keep it short.
Add "trying":
"Trying to insert 1 billion rows in SQL in under a minute".
If anything it's more interesting because it implies the chance of failure.