On 2019.2.5.62427, interactive results grid is only available for the embedded result window but not if you open the results in new window 'Open results in New Window' -> New Window
This is verified by @PaulN - https://community.alteryx.com/t5/Alteryx-Designer-Discussions/Interactive-Results-Grid-not-available...
It also appears that interactive grid is also not available if you double click a yxdb file to open it and view the content.
Would be useful to have the interactive grid in both these areas instead of just the embedded result window.