To enable proper validation between virtual texturing and opacity masked materials, a user has to check a project-level setting in order to get the material to compile, otherwise, they will encounter a compilation error message without proper guidance to correct it.
This leads to a poor UX, if the user is unaware of this setting. Ideally, this check should be enabled at compile-time of the material. Furthermore, any negative implications of enabling this setting are currently unknown or not publicly documented, so if we could investigate this during the improvement of this feature and update the documentation accordingly, that would be beneficial as well. For more information, please see the linked UDN.
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-211430 in the post.