Each GT is 400MW? that is way above the range of regular GT´s!!! the biggest units made so far are in the 250MW range for 50Hz, and around 225MW for 60Hz...
Each OEM has its own recommendations for long term storage, which are usually in the Operations & Maintenance Manual supplied with the equipment.
All the units I´ve seen when received from the factory had been shipped prepared ex-works for long term storage, that is because usually you have the units sitting on site for the foundations to be finished.
But, long term storage preparation is expensive (a customer option at the time of the order placement), if it has not been specified in the P/O, you can only blame the guys that purchased the equipment and decided that an extra 15 to 20K worth of packaging was not worth for a 30,000K piece of equipment and declined to purchase it.
Testing prior to shipment is dependent upon the P/O agreement. Sometimes ASME testing protocol is followed, sometimes not.
Testing is expensive too, so some customers waive the 100% testing for multiple units. E.g. in your case may be they decided to test only 1 out of the 3 units at the factory.
Also, testing with load is a completely different issue. Units are usually tested to nominal speed (rated speed) with no load (specially the bigger units) and checked for vibration, temperatures, compressor discharge pressure, wheelspace temperatures, etc.
Depending on the contract, an overspeed test (OST) could have been carried out too.
As the units are usually field tested during commissioning (vibration, OST) in the real, final configuration (i.e. coupled to the generator, with piping, on its final foundation, after alignment etc... the factory tests are only indicative that the unit was ok when it left the factory, with no relation whatsoever as to what the behaviour would be in the field.
Re-reading this posting, it seems like I did not give you too many answers...but more questions.
Perhaps, it all can be summarized in two sentences:
1. read what the OEM manual says
2. check the contractual documents to confirm what has been purchased and what not before raising an issue.
HTH
Saludos
a.