How to set checkboxes in Grid Multiple SelectionMode from OnInitializedAsync

[RealityMasque]

Hi, I hope someone has found a solution for this. I have a multiselect grid, & when the page loads, I'd like checkboxes checked if the items are in a separate collection of selected items. Oddly, the sample code for Grid Multiple Selection appears the same on the demo and documentation pages, but on the demo page, all the checkboxes are unchecked, but on the documentation page, all the checkboxes are checked.

Thanks in advance!