OTHO why would you leave engines sitting idle for several weeks when they should be located in a spares location in case somebody needs one immediately ?
If somebody needed one immediately, that would only help if they had conveniently gone u/s at wherever you had chosen to locate the spares.
I suspect there are enough spare GEnx engines already to support the fleet, anyway.
There is also the issue of perception - while ETH and Boeing are trying to maintain the impression (whether true or not) that the aircraft isn't a write-off, it wouldn't be good
PR to have the aircraft start to look like a Christmas tree.