When I select row in detail grid (click in cell 2) row is not selected. As side effect master grid navigates to cell 2 which cause grid scroll.
Events on detail grid does not effect master grid.
If you click twice on the same row in detail, row is selected and no scroll on master is executed.

Keyboard navigation in master-detail grids is not supported currently, see Known Limitations.
That said, we're looking forward to fix it soon. I'll leave this issue open for tracking.
Fixed in 3.10.1:
https://stackblitz.com/edit/angular-kfd2fz?file=app/category-details.component.ts
Awesome. I needed and wanted this fix for a long time.