Considering that Interdictor already has a long-standing place in the SW universe as an entirely different kind of ship (gravity well generator carriers), it only makes sense that LFL and Disney would take the opportunity that including one in an FFG product offers them and rebrand the thing as a TIE Punisher instead.
It makes sense IF they are planning on continue to referencing and use the Interdictor name in future projects and don't want to cause confusion. Say, for example, the above role you mentioned in a certain fleet-based capital ship combat game...
For the same reason Star Destroyers are renamed to Ship Destroyers in the next release.