Thousands upon thousands of chiptunes were composed on the Amiga. Hundreds of chiptune collections and so-called "music disks" were made specifically targeting this subcategory. In the Amiga scene it was a musical artistic phenomenon in its own right, and the term was solidly cemented. What you're saying is not one bit in parity with reality.

And, they're all tracker modules, whatever the genre. Chiptunes are a specific subcategory.