Why is old Source Content remaining in the Client Cache after I changed the Source in the Deployment Type?

Why is old Source Content remaining in the Client Cache after I changed the Source in the Deployment Type?

I’ve created an Application and when I created the Deployment Type I selected the Persist content in the client cache option.

I deployed the Application to my Clients and it installed successfully.

I then had to make a change to the source so I updated the relevant Deployment Type for the Application and then updated my Distribution Points.

I removed the existing version of the Application from my Clients using Control Panel and then from the ConfigMgr Client ran the Application Deployment Evaluation Cycle to pick up the new version of the Application which was successfully downloaded to the Client Cache.

However, I’m confused as to why the original source content has remained in the Client Cache when I would have expected it to be removed/ overwritten by the new version?