Rainboe,
Any significant movement of payload can cause undesirable flight characteristics and loss of the aircraft. Indeed, most of us can cite numerous examples of such instances of pilot excitement.
However, you are confusing two issues ..
(a) loading system trim
(b) load restraint
If the load restraint fails and the load ends up unrestrained .. it really doesn't matter where the trim started ... I seem to recall that John Cunningham was credited with a well-known statement relating to Comet climb angles which is jocularly pertinent to your observation ....
So far as the trim is concerned, if the normal errors are addressed and contained, then provided the TC envelope is respected, the aircraft's characteristics ought to be acceptable. However, there is certainly no reason why the operating crew might not request a particular style of loading if the company's protocols give the crew that level of detail control.