I guess, but they also say 21 days after commissioning - isn't commissioning quite a while after launch and all kinds of trials?
Normally it's keel-laying, launching/christening, fitting out, builder's sea trials, acceptance sea trials, Board of Survey and Inspection sign-off, commissioning, post-commissioning touch-ups, work up for first deployment. With some variation depending on construction method.
This article, to be kind, was not written by anyone with the merest knowledge of naval engineering. To source John McCain as your key quote? Please.
Metal in lube oil is Very Bad, but it might have slowly migrated past bottlenecks in the system and not been enough to fail the trials, finally lodging somewhere that caused propulsion to fail. There would be lab tests of oil samples all the way through trials, but depending on design they might have been fine until they catastrophically weren't. There is also always the possibility of sabotage, something NCIS would be looking at if it's suspected.
The engineers at the building yard will be burning the midnight oil to analyze just what metal this is, where it came from, and why the ship passed trials. I suspect they'll find design defects in auxiliary gear somewhere outside the main propulsion train, but again, it depends on the tasks this lube oil system is given in that class.