Is 'Just Sitting' the same as zazen?

In the Triratna Buddhist Community we do a practice that we call Just Sitting. It's described as > Just Sitting is a space of non-action in which anything can emerge. > Often the fruit of the previous practice only emerges when you stop > ‘doing’ it. And Just Sitting is the non-doing space in which that may > (or may not) happen. Just Sitting also allows assimilation of what has > just been done, and provides the necessary counterpoise to activity > and effort. Just Sitting is a matter of simply ‘being’ with whatever > happens in awareness, without attaching to it or rejecting it. Link to quote is here . I've always wondered if this is something that we've just kind of invented or adapted or is it common to other Buddhist traditions? Is it the same as zazen practice perhaps?