There is rebuild message that comes in front of Open summary. If you rebuild then of course you wait some time for program to respond but this time would be useful spent reading the summary report. We cannot as summary message is below Rebuild confirmation.

Or if you choose not to rebuild SolidWorks still spends some seconds thinking until you get control back.

This assy is huge that I open lightweight: 1Gb packed and total number of components 28000 (unique 1900)