Thanks for using Syncfusion products.
In GridControl, following kind of importing are available. They are
By default, formula cells are exported to Grid as Formula cell in both kind of exporting. We have tested your scenario using normal importing and VirtualImporting. But we are unable to reproduce your scenario at our end. Here we have attached the simple sample for normal importing and imported excel file, also tried to import this excel file in Virtual importing sample, sample location was mentioned below, so can you please provide the details of your importing code part or modify the below attached sample to reproduce your scenario. It will be helpful to provide the solution at the earliest.
Virtual importing: <Installed location>/Syncfusion/EssentialStudio/[Version_number]/Windows/Grid.Windows/Samples/Importing/Virtual Importing/cs