Hi,
I think that it's more simpler that you think. The purpose of doing an assignment is to solve a business problem, and for us, as
test takers the target is that assessor agrees that a proposed solution is efficient, consistent and solves this problem. If class diagram is split into multiple parts is is harder to understand (yes, possible, but not clear) the overall architecture.
The message from an assessor is that the level of the detail should be such that there is no need to split diagram. Sure you can put additional details there, but this won't help to solve the problem, if the overall structure is clear and right then assessor will no need additional details, you can just write that "this is done according this
pattern, enterprise beans implement required interfaces" and so on.