To explain why MCT exists, it's there to optimize MS's network bandwidth.

When you download a complete ISO, it ties up a session on a single webserver for a long time. MCT (and UUP dump) create an image by collecting UUP packages in parallel from multiple WU servers, and re-assembling them. This approach mirrors how BitTorrent clients work, and scales much better for MS.

The downside is MS offering a release-specific MCT that doesn't work as a generic tool. Plus it's frustrating every version is identically named MCT. Everyone else uses UUP dump, or ISO direct downloads if they know their exact release.