I have it in UE4.10.0, but I just got the latest UE4.13.0 and found that the material usage for landscape (and a few other options) wiped out. I set that automatically set usage in editor to TRUE and then applied my terrain materials onto my landscape, only USED WITH STATIC LIGHTING got checked.
This flag got removed in 4.13, it is intended.
Thank you!
I did a careless check upon the update notes in 4.13.0 but didn’t find anything about removal of that option. But I think you are right.