I have a sfDataGrid, and it's not expanding to cover the entire page of a sfTabView/sfTabItem. I've included a screen capture.
<?xml version="1.0" encoding="utf-8" ?>
<ContentPage xmlns="http://xamarin.com/schemas/2014/forms"
xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
xmlns:dg="clr-namespace:Xamarin.Forms.DataGrid;assembly=Xamarin.Forms.DataGrid"
xmlns:sfTab="clr-namespace:Syncfusion.XForms.TabView;assembly=Syncfusion.SfTabView.XForms"
xmlns:sfDg="clr-namespace:Syncfusion.SfDataGrid.XForms;assembly=Syncfusion.SfDataGrid.XForms"
x:Class="Photography.Handbook.Views.LensesPage"
BackgroundColor="{DynamicResource ColorContentPageBackground}"
Title="Lenses">
<ContentPage.Content>
<sfTab:SfTabView
VisibleHeaderCount="2">
<sfTab:SfTabItem
Title="List"
SelectionColor="{DynamicResource ColorMainForeground}"
TitleFontColor="{DynamicResource ButtonHomePageForeground}">
<sfTab:SfTabItem.Content >
<StackLayout >
<sfDg:SfDataGrid
x:Name="xgrid"
AllowSorting="True"
AutoGenerateColumns="False"
BackgroundColor="{DynamicResource ColorMainBackground}"
ColumnSizer="Auto"
ItemsSource="{Binding Lenses}"
GridStyle="{DynamicResource sfDgGridStyle}"
SelectionMode="Single"
HorizontalOptions="FillAndExpand"
VerticalOptions="FillAndExpand">
<sfDg:SfDataGrid.Columns>
<sfDg:GridTextColumn
HeaderText="Name"
MappingName="Name"/>
<sfDg:GridTextColumn
HeaderText="Format"
MappingName="FormatName"/>
</sfDg:SfDataGrid.Columns>
</sfDg:SfDataGrid>
</StackLayout>
</sfTab:SfTabItem.Content>
</sfTab:SfTabItem>
<sfTab:SfTabItem
Title="Details"
SelectionColor="{DynamicResource ColorMainForeground}"
TitleFontColor="{DynamicResource ButtonHomePageForeground}">
<sfTab:SfTabItem.Content>
<StackLayout>
</StackLayout>
</sfTab:SfTabItem.Content>
</sfTab:SfTabItem>
</sfTab:SfTabView>
</ContentPage.Content>
</ContentPage>