When the Project Nativization method is set to Exclusive, packaging the project will cause any struct blueprint (UUserDefinedStruct asset) to be nativized, without actually setting nativization on the struct blueprint itself.
No - same behavior occurs in 4.17.2 (CL 3658906)
Noticed "CustomStruct_pf######.h / .cpp" exist in the public/private folders respectively
Only assets specifically marked for nativization are included when method is set to Exclusive
Head over to the existing Questions & Answers thread and let us know what's up.