The short answer
Business architecture describes what the enterprise does and why (capabilities, value, processes). Enterprise architecture adds how that translates into applications, data, integration, and security that can be executed and governed.
Useful overlap
They should not compete as separate projects. In AETF, Discover informs the business understanding; Design translates capabilities into architecture layers before build.
When you need both
During large-scale change, platform replacement, or unifying multiple sectors under one operating vision.