Answer
This is a meaningful distinction for buyers who hear "AI modernization" and assume it means a rewrite project. Connecting AI to an existing system and replacing that system are two different undertakings with different cost, risk, and timeline profiles. Most IBM i shops that add AI successfully start with the connection, not the rewrite, and many never need the rewrite at all.
In practice this looks like a watsonx assistant answering plain-English questions against Db2 for i, or an AI layer summarizing ERP data for a manager who never opens the ERP screens directly. The RPG or COBOL program that originally produced that data is untouched by any of it.