Sounds like another case of you pay 4 what you get.
Pilots and cabin Crew have books/information avail on aircraft.
Engineers are expected to work from memory often, this problem of gear retractions during maint is long running and many more to follow I'm sure, think the maint manual states aircraft locking pins shoud be used during these checks.
The most common reason for the 747 nose gear retracting on these checks is the use of a non approved locking pin, it's easy to fit and remove, but the nose doors can easy remove the pin when the gear is operated in this fashion.
Interesting to know how many 747s have dropped on the floor during these operations.
A tip for anyone doing these opetations, 747s have 2 locking pin locations for the nose gear, use both is not a bad idea.!!!