As one of the co-developers of the theory here's a little more in response to your excellent question.

The river is doing work but is it making effort in order to get to the sea? Some would say it is, but we make a distinction between work and effort or trying which we argue starts with the struggle for existence, the first kind of "self-directed work" work by a self (effort), for its own benefit (functional) with respect to its circumstances (fitted). Organisms try to regenerate themselves by doing work that can outpace the natural trend toward degeneration.

So while we can always imagine that any work is trying to achieve something, we have to get beyond impressions to distinguish between systems that try and those that only appear to try.

An animist can claim the sea tries to get to the sea, but there's a perfectly good strictly physical explanation for its flow. There isn't for us organisms which is why, though in the physical sciences, effort, function and fittedness are inadmissable, in the life and social sciences they are inescapable.

Jeremy Sherman