You do not need a live internet connection to deploy OpenCore. You need internet exactly once to download the RELEASE.zip from Acidanthera. After that, the entire OpenCore ecosystem—config editing, USB creation, and bootloader installation—works perfectly on an offline Windows PC.
Need to configure your Hackintosh bootloader without a live internet connection? Here is how to download and use the OpenCore offline installer on Windows. Introduction opencore offline installer windows
The Ultimate Guide to OpenCore Offline Installer for Windows (No Internet Required) You do not need a live internet connection