Hi Mark,
Thank you for contacting Syncfusion support.
Yes, You have to create a new data source for each table to achieve the expected scenario of "Using multiple tables without joining them". After that, you can proceed to configure each Grid widget with one data source, which are unrelated.
Please refer the below documentation to create new data source,
To add more data sources please click plus button in Data sources container which showcased in the below screenshot,
Please do let us know if you need any other assistance.
Regards,
Umapathy S.