Training Stream - UE4 Game Framework Basics in Blueprint - Nov 10th, 2015

Response:

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We can’t know whether it has any dependencies that might have changed so we always compile on load.
If it is cooked content the compile on load will not occur
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As I mentioned: I suppose the projects I do are so focused on some specific aspect, they do not take a large amount of time to recompile, so I never noticed.

Sounds like this is expected behavior.