Textures That Are Not Visible in Viewport Use Low Res Mip During Play in Selected Viewport

I am unable to test the User-provided sample project in any engine version other than 4.19.2. 

Per User who reported issue:

Mips for textures that are not visible in the viewport but get showed during Play use the lowest resolution mip, in editor mode.
 
It seems that mip streaming is different in viewport mode than other launch modes. Some textures might get skipped.

1. Open attached project
2. When Play is pressed, there will be a hash (#) pattern drawn on center of floor mesh using spline mesh components
3. Play in Selected Viewport results in smooth, low-detail mip but Standalone Window or cooked project shows chalk-like high detail mip. See attached screen shots. 
4. If there is another static mesh with "chalk" material applied that is visible in editor, high-res version will be displayed on Play. 

Result: Hash symbol will be low-res during Play in Selected Viewport (if the same chalk texture isn't visible in the editor before Play)

Expected: Hash symbol will be high-res during Play in Selected Viewport