Source: p 89, The Law of Contract, 5 ed (2012), by O’Sullivan and Hilliard
If a claimant has done work pursuant to a shared understanding that the work is to be paid for, he should be paid whether or not the work benefits the defendant. Finally, as Dietrich (2001) notes, academics suggest that to work out whether a recipient is benefited, we should ask questions such as whether the defendant has ‘requested’, ‘bargained for’ or ‘accepted’ the services (see also Rowe).
Here, 'is benefitted', 'has benefited', and 'has been benefitted' all seem right and apt, but does the sentential meaning change for each? The above just exemplifies the priority of this post, the general case: what are the similarities and differences (in meaning) between: Present + adjective (what's this called?) vs Present Perfect Tense vs Present Perfect Continuous Aspect?