I made a ticket on this but thought I would post here as well.
It appears there is an issue with the latest Telerik Blazor version when it comes to adding new grid items.
I can't get it to work in my project and can't get it to work in your demo either.
Click add new employee.
Fill the info boxes.
View the added row. The Name field is empty.
I stepped through the code in my project and the parameter from the field is always null.