To be clear, and its in both the blog and my comment and on others: Multi-threaded OpenGL came much later, and is more or less a hack on top of normal GL. While it certainly has its uses, it is feindishly hard to convert an existing rendering pipeline to use "true multithread OpenGL" (that still isn't real like dx12/vulkan/etc), that as implied its better to move to a dedicated "render thread" method if keeping to OpenGL single-context. Fairly often anything still single-thread OpenGL these days has lurking demons/sync issues galore, so trying multi-context multi-thread is... eh often not worth it. Often better to just rewrite it all to Vulkan personally, but for MC especially they have a fear of increasing hardware requirements or something, i dont know, so I guess this is their next option.

I just wanted to refute that MT-GL was impossible, OpenGL is difficult and for a while was better to use DX10, but those differences (mostly) got solved. Though again, in modern times just use Vulkan (or, if you have to, dx12). Save everyone some pain :)