For best clarity, there were three things being discussed:

1. Older games, and minecraft in particular using "Main thread" for rendering
2. Older, but slightly more recent, and what minecraft is officially moving to "single dedicated render thread, off main thread"
3. multiple render threads, with one being the "submit/prime GPU context" thread. This is what was being claimed as impossible, but as I said in mine, is certainly possible though difficult. This technique was used both for DX and GL before DX12/Vulkan allowed true async multithreading.