This is a post by Evan Winter
When creating assembly level features (cuts), the system must identify what models are affected by the cut. This is based on whether the cut intersects the bounding box of a component. If Automatic Update is left enabled while creating these features, models may be unnecessarily added to the intersect list. Additional models may also be automatically added to Intersected list when assembled in the future. Left enabled, the Automatic Update increases memory usage and assembly cut warnings. To prevent these issues, disable the Automatic Update function:
1. Open the Intersect tab.
2. Disable the Automatic Update
3. Remove any non-cut models
4. Manually update the intersection list as needed.
Refer to the following 2 sources for more information
Content Source: Evan Winter/PTC