Hello Nick,
Thank you for reporting that to us. I can confirm we can reproduce this behavior locally and we should fix this bug. You can Follow its progress here: https://feedback.telerik.com/blazor/1451961-grid-horizontal-scroll-is-disabled-when-no-data-items-are-rendered. I've added your Vote to it to raise its priority and I am now marking this as a duplicate to keep the portal tidy.
Regards,
Svetoslav Dimitrov
Progress Telerik