Parallel STL algorithms requiring tbb or not?

Question

I remember that g++ 9.3.0 required to link against libtbb to use parallel STL algorithms, otherwise it gave compilation errors. I have a docker container using an ubuntu image where I have installed g++-10 only and I can use the algorithms without writing -ltbb. How can I explain this? I searched everywhere and there is no libtbb anywhere, so I am assuming g++-10 no longer needs it? Where can I read some documentation about this fact that it does not need it or is required up to version x.x.x? Thanks for clarifying.