One can not sort things like this out in an internet thread based on vague comments like "aviation sources"
The consequence to the flight "in-flight engine shutdown" by the crew occur across the flight for a variety of reasons which by themselves are as benign as this one to the safety of the flight (although a pain in the a** to the passengers)
The best I can sort out in the news report is the more reliable comment by the Qantas man David Cox which acknowledges that an engine low oil warning light came on associated somehow with a starter motor malfunction. It would require a degree of speculation without more details to understand but the understanding is only of importance to the preventive action in the future which is far removed from the lot of most casual readers of news print.
I seem to recall a starter failures in the past year on an other installation where the starter rotor disintegrated and punctured the engine casing itself.
I feel for Qantas but the only way out of the news is a stroke of really good luck or a smaller fleet BTDT