I have been told by driver vendors that GL multithreading does not work on windows, yes.
D3D multithreading works (even, to a lesser extent, with D3D9!), and this is one of the reasons why our D3D9 renderer is dramatically faster than our GL one - we can offload a subset of rendering work to helper threads instead of keeping it all locked on the thread that owns the window.
TF2/etc do offer a multithreaded rendering option, but IIRC on Windows their engine still uses D3D. Also, note that it's an option, because the feature used to be very unstable (still might be, actually) - I suspect people using the GL version of those games may have to disable it on certain hardware/driver configurations.
D3D multithreading works (even, to a lesser extent, with D3D9!), and this is one of the reasons why our D3D9 renderer is dramatically faster than our GL one - we can offload a subset of rendering work to helper threads instead of keeping it all locked on the thread that owns the window.
TF2/etc do offer a multithreaded rendering option, but IIRC on Windows their engine still uses D3D. Also, note that it's an option, because the feature used to be very unstable (still might be, actually) - I suspect people using the GL version of those games may have to disable it on certain hardware/driver configurations.