I cant comment on the reason behind the oil loss as it is the subject to several investigations.
To answer your question how about this....
When a PAN PAN - message is sent, there's no immediate danger for the safety of the passengers, crew or aircraft.
MAYDAY, however is an indication of a dangerous situation that has risen and immediate action is needed.
So NO it was not an emergency, it was a precautionary measure. Realistically the aircraft could have held for several hours if required or not even told anyone and continued and no one would be the wiser. If anyone learnt from someone else it would be this incident
Airnorth Regional E170 near Darwin on Mar 24th 2014, engine shut down in flight | AeroInside
They did not tell anyone, no pan, yet it blew the crap out of the engine and was on the ground for 10 days and it created a hoohar of sorts Airnorth even had to cross hire Alliance to maintain schedule integrity. Jetgo on the other hand are transparent to the incident, the company safety systems are robust enough and so are the crew actions and policy, and the aircraft was serviceable within hours of the replacement part being sourced.
To infer here in this forum that there is something untoward happening, when the facts have been provided in a transparent manner, leads the proponent of that rumour down the slippery path of what happened in another thread concerning the same company.
As far as the company and the regulator are concerned its now time to await the report and see what was the root cause then take steps (if any are required) to mitigate the issue and prevent it from occurring again.