Technician reported communication issues and lack of clarity with documentation caused an aircraft to be released for service without all of the required checks performed on a recently installed engine.

Narrative

On DATE I was performing test no.7 pretested replacement engine-operational test per AMM 71-00-00 on aircraft X #2 engine at the ZZZ. We had completed step B(10) The Engine Anti-Ice (engine in operation) System Test and were moving on to the test of the Engine Vibration Monitoring System. Reading through the paperwork we came upon a statement saying that a vibration test is not necessary if you do not do maintenance on the fan. We were working with a pretested engine that tells me it came from the vendor already tested. After going through the ELB and not seeing maintenance done to the fan my coworkers and I agreed that the vibration tests were not necessary as per the paperwork. We did not know at the time that only the propulsor came from the vendor and the engine shop had to install the fan frame; blades and spinner. Now knowing that any 787 engine installed on the aircraft has been built up at the station it will require a vibration survey I believe that the statement 'a vibration test is not necessary if you did not do maintenance to the fan' should be removed as it is misleading especially if you do not know that the engine is assembled at the station by the engine shop; as was the case with my colleagues.