While that may be true, it's not what Spirit has said. They have reported that "...a non-standard manufacturing process..." was used to assemble "two of eight points where the vertical fin is attached to the fuselage.".

As an example; this could be as minor as using a riveting tool that hadn't been inspected on the correct schedule but was still operating as expected. It could be far more serious; perhaps that riveting tool was operating at a dangerously low pressure resulting in a poorly attached vertical fin.

We don't know yet. If this had happened before the 737 Max debacle I would have complete trust in Boeing's and the FAA's assessment that "...that there is no immediate safety issue.”. As it is I can't help being a little skeptical, that loss of trust is a real shame.